The Primo rim is excellent, but it only has one style (at least as far as I can tell on danscomp) so for a single designed rim, it is very good. It isn't a cheapie rim that'll fall apart on you. But, it is also 50 bucks, so it isn't a 'bargain' rim either.
Alex is a company that makes a bunch of rims... and some of them arent very good. But, for 30 bucks you can get a chrome plated 48 or 36 hole rim which is a real bargain. They also have some really nice rims using the latest rim design technology. Their best are very similar in quality to the Primo rim and around the same price.
So, it is 100% personal preference which one is better - because neither really is when you are paying the same amount.
In fact, I haven't really seen a $50.00 rim that has been piss-poor in quality. On www.danscomp.com ANY rim 50 bucks or more is about the same quality and is of very high quality.