Efi is tonnes better and more reliable, I'd say the tuners are talking crap but who am I to say. I have owned an efi turbo engine for about 3 years and its been brilliant. But tbh I've never owed an mfi RS turbo lol a lot of the people I know who had mfi Rst had a lot of probs. I bought my engine with all looms ecu turbo, and LSD box for 350 ( lucky find) turbo tank n pump for 50 and hoses for 150 all in samcos and front mount and ally rad for 300 together with all other bits n bobs and a tune it probably cost me around 1200 fitting and wirings the easy part. I'd never done anything like it in my life but just got on with it to save me money lol. I ain't no mechanic just an electrician but anybody can do it. Use www.rsbible.com for wiring I got quoted 1000 to wire mine by auto electrician cheeky git lol also try and aim for ofab if u can rather than ofac.
Most people can help you on here though mate.