Diff between TVs that can attach to pcs & Monitors that have Tuners

i'm looking to purchase a flat (lightweight) 15"-17" LCD TV/PC Monitor (it has to fit in small space when travelling). Is it better to buy a PC Monitor which has a tv tuner or get a TV which has the ability to connect to a PC? I went into an electronics store and asked this question and was told that an lcd pc monitor has a much higher resolution so would be better but i'm wondering why they are so much cheaper ($300 vs $500) than LCD tvs which will hook up to a pc?

if there's a good article on the web that explains this, I'd appreciate it also.