My advice... do a bit of research into the different poptops and then go and visit a few fitters in your area to confirm you're happy with what that specific roof offers.
Then once you've made your desicion ask the forum for feedback of local fitters and also non local but highly respected fitters.
A good roof is a few grand and ideally you only want to have one hole cut into your very expensive van. No offence to anyone on here but only you can really decide which roof suits your needs.