Here's the newbie mistake... trying to get too much with too little. Again do some research on components - on these bikes they are very low end which means they probably won't perform well and won't last that long. If you plan on doing mellow trails or bike paths you should be fine; less chance at epic failure of equipment. But again if you want to do real trails, get a better bike. Cheap full suspension is really not the way to go but then again I am fussy... if you want full suspension then start looking for a used bike...

PS can't say the Motebecane is a better bike. Since its a hardtail less chance of frame failure but its still low end, same components as the Gravity. But i understand having abudget and trying to stay in it. Good bikes are expensive even what I call good low end bikes (I figure $800 for a hardtail and about $1300 for full suspension) if you buy new.

BTW is there a shop nearby that rents out or loans out bikes for you to try?