Assuming you identify an area for SaaS for which there is minimal competition, I would tend towards SaaS because it probably would take less effort to get to MV

Assuming you identify an area for SaaS for which there is minimal competition, I would tend towards SaaS because it probably would take less effort to get to MVP and then with some upkeep it would have a longer revenue generating life. Games and Apps need to be more polished to sell (if at all) and then if you don't have new releases new sales will rapidly decline. All successful apps and games end up getting a lot of on-going upkeep. BUT ... in either case, it really depends on the marketing investment (money and effort). It's rare to create something that just sells itself.