Honestly I would go for a PC
The perks of having a PC are numerous playing games, work, watching videos, etc
If you are a gamer the obvious choice is to get a pc with $700 would could get good set amount of parts that could fit your need, or if your not a gamer you could save some money on buying (for say) an motherboard with interrogated graphics.
However with Tablet you have portability and honestly most of the features a computer could have, there may be even more perks, if your an artist for say, you could carry around the tablet draw the landscape, etc.
So personally I would go for the computer building one if very fun! (Making my first one now) and you can keep upgrading it in the future making it a very good investment, either way good luck maybe the other people answering will have better answers XD not good at this goold luck!