well, i live in texas and i have never heard of metro pcs. however, it all comes down to reception in your area, customer service and overall cost, really. and it all depends on what you want to use the most, texting, calling, etc.http://www.cellreception.com/
is a good site to find what carriers are the best in your area
i looked at it a bit on google, there are some pretty bad reviews but that can be said for a lot of companies. people do seem happy about the concept of "unlimited minutes" that metro pcs has. i don't know if that's the standard plan though.
i'd say your best bet is to google metro pcs reviews and see what people have to say. there are a lot of sites that have reviews, and a lot of mixed reviews on those sites.
i use verizon wireless, recently switched from cingular/att (dont recommend!!!) and it has great reception here and it seems like its pretty affordable.