My Pleasureway Traverse is designed similarly to a Westy and has a pop-top.  It's useful on occasion but the fiberglass roof is challenging to mod according to PW.  I wanted to have a Fantastic vent added but PW discouraged me from that.  With the top up, especially with one that has 14 year old fabric, it's not weather tight.  Every season I have to patch, spray, etc.  It is terrific having standing headroom in a camp spot to be able to stand, change, cook, etc.  But in the future (I was 57 when I bought the van in 2008, I'm 65 now), I would much prefer either a high top conversion or, better yet, a tall top van.  The older you get, the less crawling around you want to do.  That said, I do a fair amount of stealth camping while on my way to and from a place and the top stays down.  Bottom line, I would not buy another pop-top van.