Not the smartest question I know, but exactly what is the difference between 4x and 16x blank DVDs?
I assume it has to do with the write speeds? But I’m interested in how will these differences impact my burning?
I have faith in you, fellow Dopers! 
I believe if you try and burn on a 4x disc at a speed higher than 4x, you’re prone to write errors. So a 16x disc can be written on at up to 16x.
In some cases, you’ll get away with writing 4x speed DVDs at slightly higher speeds; in other cases you’ll make some useful drinks coasters - when you write data is to recordable DVDs (and CDRs), the laser causes a local change in a layer of dye, but if they disc is spinning at a higher speed than that at which the disc is rated, the region passes by too quickly for the laser to be able to effect the change in the dye and you end up with a low-contrast pattern of bits, which other drives may or may not be able to cope with, or you end up with data that is simply not properly recorded on the medium at all, which is a coaster.
I presume the higher-rated media contain a dye layer that is faster to react.
I assume it has to do with the write speeds? But I’m interested in how will these differences impact my burning?
The higher the X number, the faster the disk can be written. However, the disk is only half of the equation. If your burner only writes at a maxumim of 4X then using a 16X disk isn’t going to make the burner burn any faster. It isn’t going to hurt anything to use a disk rated faster than the burner, but it isn’t going to help anything either.
Also…to get the best quality data transfer you really should burn at a slower speed. Just because your burner burns at 52x doesn’t mean you should burn that fast.
Slower is better.
So if it’s better to write at a slower speed then it’s definately the x4 discs I’ll be getting as I don’t mind waiting a little longer for them to be done and they’re only £16 for 50
Oh, and as a sidenote, how can I find out what speed my burner is and what format it burns or whatever? 
What’s the brand and model? You need to check the specs. You won’t find the info written on the drive. Good advice to always burn at half of your maximum speed if you want to avoid getting coasters.
It’s a TEAC DVD+RW/DV-W58E that came with my Dell, I have a horrible feeling that it only burns in - though. 
Put your burner’s model number into the search at VideoHelp and it should cough up some specs.
:: pause ::
TEAC DV-W58E. Hmm. Burns DVD+R at 8x and DVD+RW at 4x. Does not burn DVD-R, DVD-RW, DVD-RAM, or DVD+R dual layer.