Being an Everton supporter with a lot of time for Villa I've read this latest discussion with great interest.
My view is that both clubs have a "bandwith" - Villas currently being from mid-table Championship at worst to top 7 in the PL at best within 24 months. Quite a huge spread of 20+ league placings, but given luck, finances and players gelling to a team not out of the question - and vice versa. Evertons range is narrower - probably 14th-3rd - and, as each place upwards becomes progressively harder, more likely 9th-5th. So Villa can get on par with Everton within a couple of season, b