I own both REO Grand SL and Provari and MVP
There have been changes to the REO line since this thread began.
The Reo has been updated with Low Resistance Contacts, Internals and the performance is very close to the top of the line tube rockets.
They have added a LP [Low Profile Version] which has a very shallow wider cup. It's dual use and will allow you to use virtually any RBA on the market as well as a bottom feeding RBA or Atomizer. So you can buy a REO Grand LP and use your favorite dripper on it.
I bought a Reo 7 months back and returned it because the V-Drop under load was atrocious. The new Sub Ohm Reo Grand has solved every problem that caused me to return the APV.
By the way, my Provari gathers dust as a nostalgia piece, and my MVP because of it's huge battery life is the one I use for certain situations.
In my opinion the reasons to buy a Provari and the reasons to buy a Reo Grand are similiar.
The Provari is very reliable and has warranty and can be sent in to be repaired after warranty expires.
The Reo Grand is also reliable. Reos Mods sells a rebuild Kit, that can be used to repair it, or you can gut the unit and have essentially a new unit for just $25.00.
Nowadays there is a vape shop in many areas that will build an atomizer for you. Sometimes just for tips, or others charge $5.00-$10.00, so you can own and operate a Reo Grand without ever having to learn how to make coils.
Myself
I use the Reomizer 2 from Reos Mods
FC-2000 Ceramic Wick that I purchase at Tank Ecigs,
FC-2000 Porous Ceramic Wicks
24 Gauge Wire that I purchase at Temco and it's easy as heck. I make a Wick in 15 minutes and it lasts for more than 3 months.
There are some very powerful batteries that have come out in the past year.
The new Sony VTC5 30 Amp 2600 will give you a good 10 - 12 hours on Subohm Vaping
They hit hard and have alot of Stamina.
Another favorite of mine is the Panasonic NCR18650PD not as hard a hitter, but stays in the zone for a really long time.
I've found that the difference using the Panasonic is only around .2V from full charge to steady voltage. Gives a very consistent vape.
So even though the units are different and used differently, the basic premise of wanting a reliable unit that will be an investment for many years to come applies to both and would appeal to the same type of person.