I’m sure some cyclists think that, but like Rick, I don’t care what you ride. Ride whatever you like. However, you asked if there were benefits besides frame material and suspension between the cheap bike and the real bike. And I answered your question as best I could. There are extremely large differences in the quality that make noticeable and substantial differences to how pleasant they are to ride. To be honest, I don’t think suspension is even an issue. Unless you’re trail riding, you have no need for a suspension fork (well, okay, I don’t know about the pothole situation in your town :)), and unless you’re downhilling, I don’t think you gain anything with rear suspension either.
Weight isn’t the half of it. I’ve ridden the department store specials, and I’ve ridden mid- to high-end stuff. Well - depends on what you call high end, but my main ride is an old Stumpjumper M2 with AMP forks which cost me Cdn$1350 plus $600 or so for the forks, back in the day. Not exactly bottom of the barrel material, though one can spend a lot more without any difficulty.
In my experience, the braking power on el cheapo bikes is downright scary compared to the stopping power of good cantilevers on decent rims, and that’s only if they’ve been set up by someone who knows how to do it - otherwise they’re even worse, howling and squealing because they’re toed the wrong way, and improperly positioned to take advantage of what little leverage the cheap brake design gives them. The rear derailleur that bike has - flat parallelogram instead of slant parallelogram - means that the cage on the derailleur gets further from the freewheel cogs the higher the gear you’re in (with slant designs the cage moves up as it moves out, more or less tracking the angle of the cogs on the freewheel), and once the chain is worn the least little bit it has simply too much lateral flex to shift accurately on the outer half of your gears. You’ll have to overshift to get the chain to jump, and then move the shifter back to center the cage. This is at least possible with the SRAM shifters it has, unlike some of Shimano’s Rapidfire™ jobs, unless they’ve changed their design since I last used them; however, it’s a pain in the butt, renders the indexed shifting useless, and it makes the bike far less rideable.
The weight, which, as I said, isn’t the half of it, nonetheless is a big part. Until you’ve ridden a light bike - particularly one with light wheels - you just have no idea how much livelier it feels. They float over rough spots, accelerate effortlessly, and top out far faster than you realized you could ride. Not, I should hasten to add, that $300 will net you a truly light bike. However, it will almost certainly have alloy rims, which make a substantial weight difference to the most weight-critical part of your bike. Paying attention to weight when choosing tires makes a difference too. This is because that rotating weight around the perimeter of your wheels is the mass that has to be accelerated the most. Weight on the frame is much less important, though certainly not negligible.
If you plan on going offroad (I suspect not, given what you’ve said), things get even worse. The weight of that thing would make it next to impossible to muscle around on a trail, and simple strength starts becoming an issue. In spite of increased weight, most parts of the cheap bike are actually weaker than those on a more expensive model. I recall seeing a “review” of a Huffy in one of the mountain bike magazines, where they’d ridden it no differently than any other test bike, but had pretty much destroyed the thing in a single afternoon. The handlebars had bent alarmingly, I seem to recall they’d taco’d a rim (though to be fair that’s not all that hard to do to a good rim on a gnarly trail, either), and various other bits had failed. Of course, those guys thrash bikes pretty hard, far harder than you’re likely to. Nonetheless, durability is something that does matter to a degree no matter how gentle you are with a bike.
So basically, as I said in my first post, you get what you pay for. The Walmart special will get you from A to B. However, it will require double the effort that a $300 machine would to make the same trip, and will operate in a generally inferior fashion. It’s entirely your call. If you like, go to a bike shop and take something out for a test spin, to see how better bikes ride. This will help you determine whether you think they’re worth the higher price, which is the question that matters. If you decide to go with the cheap bike, I do have one piece of advice. Look around for something without a suspension fork. The sort of suspension fork you’ll get on a 60 dollar bike is worse than no suspension at all. It’s just extra weight and some moving parts to go awry for no benefit.
But seriously, you get what you pay for with bicycles, for the most part. A few key differences between the Walmart special and a $300 Trek or what have you: