We've got a Westy hightop and it's great. Some of the positives - all the extra storage space up top which you retain even while you travel, ease of camp setup with the kids, quieter and warmer due to insulation, plus the ability to standup most of the time. A couple of extra benefits - you don't lose your upstairs sleeping area in really foul weather when a pop top might need to be collapsed, and in terms of the stealth thing, any stuff you do store up top cannot be seen from outside even if you leave the curtains open. In terms of comfort, I regularly sleep up top alongside one or other of our kids age 10 and 12 and I'm near 6ft, so I wouldn't worry about that unless you have lots of basketball players in your family.
On the downside, apart from the obvious thing about not being able to get into garages, etc, which we only very occasionally would love to have, there are a few other compromises worth mentioning. The access to the top, particularly in terms of getting up there with the bed extended is a bit more constricted than a pop top would be. Also high tops can develop some pretty grim issues with corrosion at the interface between the fibreglass roof and the van body if the gutter sealant goes or the skylights leak. Finally, if you travel a lot on the continent you may get charged tolls for a commercial vehicle rather than a car due to the extra height.
On balance though I don't think we could be persuaded to change to a pop top.
