I don't limit myself to a single App. I currently use Zwift, Rouvy and SYSTM. I've also used Bkool in the past, but dropped it last year in favour of Rouvy. They all have different strengths and weaknesses. The cost does add up, but with annual discounts and the odd sales discount it's not a huge expense in the overall scheme of things. Rouvy is my favourite for real video based rides, Zwift for online group rides & events and SYSTM for structured training plans. I wouldn't like to pick only one platform, but I do a lot of indoor training all year round and get my money's worth out of all of them.