What are the drawbacks of a gevey sim unlocked iphone 4s?

I have never used an apple phone ever. I can't afford to buy the factory unlocked iphone so i was thinking to buy the gevey unlocked one. Can someone please tell me the drawbacks and answer these questions in simple language?

does the gevey unlocked work like a jailbreak or a factory unlocked?
can i download apps directly from the apple store and save music on itunes?
is it legal to gevey unlock an iphone?
is the iphone 4s a good option to choose over the s3(just sold it, i didn't like it)?
Some people say gevey unlocked iphones don't get full network signal bars, will i have to face problems in messaging and calling?

Honestly, it's not worth the hassle, do it if you want but you could just use a cheap online unlocking service that will permanently unlock your phone forever in a few hours after purchase…