Generally at those price points you are looking at bikes not really designed around MTB more for puttering around some easy grass or gravel trails on a heavy bike. However it does look like the two bikes you are listing are maybe used at those prices but certainly an air fork is generally going to be better than a cheap coil fork. The fork is kind of the most important part and generally with a good air fork you will have decent parts on it as you have with the second bike.

If the bike has thru-axles and an air fork it is likely a decent candidate for upgrading down the road if you don't want to just get the bike you want new. However I recommend getting the bike you want from the get-go because upgrading is significantly more expensive.