disc brakes have their advantages and disadvantages to name a few advantages: If the wheel is not completley true/ somewhat bent you dont have to worry bout the brakes rubbing, They are a good investment if you can afford good ones getem they last awhile.
Now for some disadvantages: The disc brakes on most $500 bikes are trash if you don't go for good brakes aka hayes stroker or juicy or some hydraulic ones then you are better off getting standard calipers. Taking care of them if they are slightly misaligned is a pain in the @$$. The pads are expensive. If you get hydraulic brakes the bleeding process is expensive.
But as said earlier you are better off getting a better bike than discs cuz the shop i work at we make fun of those people who buy the bike for the disc brakes and don't realize what they sacraficed for the appeal.
And Remember you are just starting if you want to upgrade you can most good entry level mountain bikes have adapters for discs.
Best of luck