Alltel HTC One V vs Straight Talk Samsung Galaxy Proclaim?

So I have just started a new job and decided that, since I'll have a little extra cash, I'm going to buy myself a smartphone. I've never had a smartphone - just basic cell phones - so this will be my first. My only options as far as services is Alltel, Verizon, and Straight Talk - I live in rural Georgia and cannot get service from T Mobile, AT&T, Sprint, etc.

I'm trying to decide between two phones/services: the Alltel HTC One V, which will cost me around $75 a month for unlimited talk, text, and 2GB of data, or Straight Talk's Samsung Galaxy Proclaim, which is $45 a month for unlimited talk, text, and SUPPOSEDLY unlimited data as well (though I have heard that after 2G they drop your service or something).

Verizon is far too expensive for one phone, and I've always been an Alltel customer - many times I have services where my Verizon friends do not. So Verizon is out of the question.

My concerns are as follows:
- Is the Straight Talk $45 unlimited TRULY unlimited data? I have no idea how much data I'll use - I primarily would use my phone for apps (Twitter, Draw Something, Temple Run, etc), checking email, light web browsing, and moderate texting. I most likely won't be streaming any music or videos - I prefer to leave that to my laptop.
-The above issue also apply to the Alltel phone - my cheapest data package is 2G, and I'd rather not pay $50 for 5GB (I'm too cheap). So the data usage issue rears its ugly head again.
- My final concern is that the Alltel phone is a contract phone, and I'm not sure how long I'll be at this new job. I will be graduating college next spring and most likely moving off to a different university to continue my studies. I may be out of a job for a while, so I may not be able to pay for the phone - and I know cancelling a contract early is a pretty penny.

Any helpful advice or first hand knowledge of either phone/plan is greatly appreciated.

Thanks!