All else being equal (let’s say, the price was close enough, or you’re rich enough, that it doesn’t matter): if you’re planning a wedding reception, would you hire a random band that you found on a website; or would you hire a random DJ that you found on a website? Also assume that both are amenable to tailoring their song selection to suit your tastes.
For simplicity, a DJ, or even just an iPod playlist, are, to me, perfectly fine options.
Bands can be tricky; are you hiring them sight unseen or are you taking the time to actually audition bands, because trust me, recordings on a website and seeing them play live can be two wildly different things.
Given a choice, personally, I would just make up an iPod playlist. I already know what I like and what I want to hear, why not just hear it from the original artist(s), and not some local wedding band playing covers?
I attend a lot of weddings (I’m in the industry), and a good band gets the dance floor moving much more than a DJ, in my experience. (Though a good DJ will do a great job, as well, to keeping the energy going. I just find that people seem to respond more to really good live music.) Luckily, most of the bands I’ve seen have been good. If you’re finding a band that is coming in at the same price as a DJ, I’d proceed with caution. They may very well be good, but I would at least want to drop in on them playing a gig to get a sense of their work in person.
I can’t imagine hiring either as a random choice. If I hadn’t heard someone myself or gotten a recommendation from someone I trust, it would be like buying a car I’d never seen or driven. Yeah, it might work out, but for a wedding I’m pretty sure I’d want to know what I was buying. Especially if you’ve got specific requirements for music styles, whether you want the DJ/band to make announcements/comments or just make music, whether you do or don’t want a Chicken Dance - you need to know that whoever you hire will comply.
I think Id either rather have a DJ, or both. It seems like a DJ is generally more versatile, although I suppose a live band could also switch out with a playlist for requests and breaks. I can’t see wanting a band unless I have enough money to hire an actual “favorite band of mine” as opposed to a generic wedding band. On the hand I might do it not for my own pleasure, but just on principle to support live musicians. And also because, how else will Ted finally meet the mother?
the band has too many variables to go wrong and can’t play modern day dance music. Go with the DJ and the 1 man show
At least a lousy DJ will still be playing pre-recorded music that you can be sure won’t suck. If I’m picking blind and don’t get to meet them first, I’m picking the DJ and handing him my playlist on a flash drive or something. There’s just too much risk when hiring the live band - who knows what I’m getting?
An Ipod playlist and free access to the equipent for bored relatives.
more importantly: free access to the volume control on the equipment. Why the hell are all the weddings I go to so damn LOUD?
As a guy in a band I must respectfully disagree. To quote the sage advice of P.J. O’Rourke “Volume is everything. If the volume won’t kill songbirds in the yard and make the dog wet, it’s not going to be a real party.” 
I’ll make it a point to skip your reception, then. As a musician, I vastly prefer a live band, even a mediocre one, to most DJs. That said, any good DJ has a talent that I admire (and don’t have), involving reading a crowd, good timing/dynamics, and really knowing a wide variety of music remarkably well. Your playlist won’t read the crowd, and unless you’re very unusual, your party mix will ignore about half the audience. (After all, you only talked about what you like and want to hear. You’re not the only one there. A party is for the guests, not just the hosts.)
Why not hear it from the original artists? It sounds the same every time. There’s no audience interaction. There are no surprises. (Any good musician will tell you that good music is a balance between building expectations and surprise.) And as mentioned above, people respond better to people playing than to recordings.
But I’m assuming we’re not picking something at random without checking them out, or at least depending on the recommendation of someone whose taste and sense you trust.
As a guest, I’d far rather have a band to a DJ, but I’d also far rather have a mediocre DJ to a bad band. As a pro-am musician, I don’t have the loathing for DJs that some (especially small-time pro) musicians have, since I haven’t lost any potential gigs to them, not that I’d notice or care or that would matter. I can get as many gigs as I’d like; the harder part is avoiding gigging more than once or twice a month.
When younger, I had more resentment for stereos, since I’d usually have an acoustic guitar handy, but as long as a stereo’s playing, no live music is going to happen. I remember enjoying visiting bars in remote areas of New Zealand where goodness knows why but they didn’t have stereos running constantly, so I could sit at the old upright piano, and meet people and get free drinks all night. Never happens in the US: the piped music is always going.
I’m a musician and I believe in supporting live music, so I voted for the band.
I’d rather have a mediocre band to a mediocre DJ partly because I’d be able to control the genre of music the band knows. A mediocre DJ would bring crappy music from all different genres and would play it all, even the crappy stuff from crappy genres (not just crappy stuff from the genres I like.) The DJ might also do those standard wedding embarassment tricks which I hate to see or participate in.
I am in a band, and have been a wedding DJ, so here’s my 2 cents…what do you want? DJs are compact, neat, have all genres of music, and can basically play everything you want at a much cheaper price. The trick is to make sure you’re in charge of the reception and let them know what you want up front. This gets rid of the aforementioned lousy music and stupid wedding tricks. The thing is, many people want the cheesy wedding songs and stupid wedding tricks. Just make sure the DJ doesn’t take over with his “knowledge” of music.
Bands, on the other hand, can be complicated, have volume issues, and may have a limited set list, but nothing rocks out like live music. A good band can get a party jumping more than any DJ (assuming you’re not into house or dubstep!). Hell, I’ve seen polka bands kill at weddings. That said, an experienced wedding band should have a pretty good set list and have the volume under control. Most bands would have no problem with you “auditioning” them at one of their gigs.
So, looking at your scenario where cost and playlists aren’t an issue (considering they are probably the two biggest issues in this decision), I would lean toward the band. The only reason I’m not 100% behind it is that you stated it’s a random band found on the internet, and they could plain suck. You can actually fix a bad DJ.
Band, as long as they’re decent. A DJ just increases the douchiness 200%. They don’t really have that much work to do compared to your drunk uncle with an iPod, he’s just more likely to play Freebird 3x in a row. I’m still 
about the wedding I went where he played a song about ejaculation and sweaty balls, and another about ejaculating on a woman’s back and pasting a blanket to her back. Bands are classier, although you still run the chance of Jon Lovitz’s band from the Wedding Singer. NB: I think dancing is the worst part about a wedding.