The first rack you posted about, the tilted "arm" rack--I would say it may be easier to take off and store in a smaller space than the one built by George2615. I'm not familiar with that particular brand of tilted rack, but the one I've seen mounted to a plate in the bed of the truck and also bolted to the bed rail. There was an upper, removable section that then bolted to the base. If someone wanted to steal the upper section, then I guess they could unbolt it.
The rack posted by George2615 is well done. It appears wide enough to carry quite a bit. It looks like it would be very sturdy, and might be easier to mount to the bed rails than having to make holes in your truck bed.