if you are itching to get disc brakes immediately... then go for the 4300. although the smart decision would be to go for the 4500 and then upgrade, unless you're never going to spend money on your bike after purchasing it. I personally recommend saving up for Avid bb5's, new or used. they are amazing mech discs and a far cry from the tektro io's. My friend's io's turned out to be worse than properly maintained v-brakes. then he got hayes hydro's, so he's fine now. the final decision is always up to you and your budget.