If you are considering a certain boat, find out what engine and drive setup it has. Most are great, but some would be best avoided.
I am a Volvo certified tech, I also wouldn't own an IO that wasn't a Volvo. I also work on both Mercruiser and Volvo, probably more Merc than Volvo.
Drive parts cost more, but with basic maintenance and care, seldom fail.
If you are in an area with no Volvo techs, that could be a problem to if you pay to get everything done. If you do things yourself, in most cases having a dealer near by is not necessary.