I want to buy a new computer and i can't decide between two.Which one is better?

Go with the first one. Since the processor is i5, it automatically makes it around 3x faster than the i3 which in my opinion is very slow and Minecraft would most definitely lag.

Go for no. 1. Slow processors suck.

Neither of those graphics cards are what I would consider "good". So you should be open to performing upgrades in the future. Although you can run minecraft on a toaster, my 4 year old phone runs it. Both processors will last you a while, however that i5 is about twice as fast. Not that you need the extra speed, as I said, they're both fine. 6GB RAM is perfectly fine, and RAM is cheap so if you want 8 it's only about another $20, if that. If it was me, I would buy the first one. Sell the graphics card, and get a GTX 750 or better. But the 750 is my personal favorite at this point in time, it's about twice as good as the 650 and only around $20 to $30 more.

Although, I would build my own computer (I did). It's the best way to go if you know how to put one together. Which isn't hard to learn. Just don't work on carpet, or short your components.

Verdict: For what you want they are both fine. But if you ever try to play something harder to run than minecraft, get a new graphics card. I would go for the first one, then upgrade somewhere down the road. The processor on that one will last you longer, you really don't need the extra 2 GB of RAM, and both graphics cards need replacing. The 650 will sell for more than the 630, so it'll make your upgrade that much easier.

It depends on your usage. If you use it mostly for playing games and video editing applications etc. I3 processor is enough. If you have more things to do then better go for i5. And its also depends on your ability to purchase. If you can afford "easily" better choose first one