The verdict
If you run a SaaS product and users get confusing or duplicate emails, I'd pick Loops. One contact list, one place for events and one set of rules is a better base than two disconnected email systems.
If your problem is that prospects do not turn up to demos, pick eWebinar. A recorded session that runs in any time zone fixes attendance faster than rewriting emails.
If you must choose one and your product already has users, Loops usually gives more return. Add eWebinar when one session is repeated often enough to justify the setup. The two combine well, because registrations from eWebinar can feed contacts into your email flows.