GTX 750 VS. Radeon R7 250X

I've recently determined that I have a budget of around $400 for a gaming rig, and I am stuck between the following cards.
MSI GeForce GTX 750 (NON TI, 1GB) - $99.99
MSI Radeon R7 250X (2GB) - $99.99
What card is the better card? I will be primarily running CS:GO, Portal 2, TF2, StarCraft II, and will be buying more modern games as PC will become my main platform.
Thanks for your time, have an awesome day!

I'd get the 250x over the 750 because 2x the vram which is important these days. However neither are really gaming cards, I'd suggest putting $40 more away and getting this

Save up and get an R9 279. They can be had onsale for around $120-140. It is really worth it and will absolutely kil either of those cards.

Just get that, done. Honestly, the 270X will play anything at 1080p at medium to high settings, no problem. I actually have 2 HIS Turbo 270X's collecting dust... Maybe I should sell?

@serenity you should definitely grab a 270/270X (from @Beezleybuzz if he is willing to sell :D) . I feel like you will really regret not grabbing a more powerful card soon after you build your PC.

You willing to buy used?:

The GTX 750 is the better card, however, for two days you can get a R9 290x for $189.00