Hmm, I do not see this as an "either/or" proposition.
While there are adherents to each device, it really comes down to YOUR preference.
Though I have mech mods and RBA/RDAs that I build my own coils for, I generally prefer the simplicity of having a vv/vw variable power regulated mod. Simply more safety built in and I can adjust the strength of my vape without having to replace coils to do so...but then perhaps I am lazy!
While the Provari is a fine device, from a price vs. vape-quality vantage, there are a slew of variable power devices which cost a fraction of the price and provide just as good a vape.
If you are a new/newer vaper, I'd recommend trying a Vamo, SID, or other lower cost, full featured regulated mod ($50 price point) before buying a Provari. See if that is what meets your vaping needs, and if so, then you may decide to get a Provari...or not.
Same with a mech mod. Plenty of perfectly vapable $29 - $49 models to start with.
Based on the nature of your question, I get the impression that you are at the "exploration" stage of vaping...and that is good! Until you really develop your own preferences, why spend substantial coin on a higher-end unit?
PS - Size is not a matter of mech mod vs regulated...plenty of both smaller and larger mods in each format.