Both are complete association management systems, so you should choose based on which one fits your operations best, not just on which is more popular.
YourMembership can make sense for small-staff associations that want membership management, a hosted website, events, online community, e-commerce, workflow automation, and reporting under one broad AMS relationship.
Member365 tends to fit organizations where membership, reporting, payments, engagement, professional development, and complex operational rules need to share a connected data model, with more visibility into pricing before the sales conversation begins.
