Ok here goes.
You can't edit it so go to File, Download as and then you cal play around with it.
Room 1 is where you play, Room 2 is where you are planning to move or want to compare.
All bold cells have a formula and other cells need to be input.
I'll run you by how it works using NL 10 at Pokerstars comparing with William Hill for example.
I enter the bb as 0.10 for Nl 10, Rake % and rake CAP are very easy to find, just google the room name followed by rake structure and you'll get it.
For Stars I enter 4.5% and $1.50 as the respective numbers, do the same for William Hill.
The Room CAP pot size is the amount of bb in the pot when rake CAP hits, quite self explanatory.
Now you need to go into your database, filter for hands that were below the CAP size on this limit. In HM2 you'll find it in More Filters, Advanced Filters, Other, Final pot size in bb is...
I'm sure PT guys will manage to find it too.
So I input the number of hands where final pot size<333.33 and the avg. pot size in that sample.
Now same filter for number of hands above CAP.
You get total rake paid and this is rake paid by all players across all hands where you played. You contributed a certain % of this rake. Most rooms now use weighted contribution method to calculate rakeback so this should normal out as the assumption is lets say you payed 10% of the total rake on Room 1 and played same hands on Room 2 you would have still paid the same 10% which in absolute terms would be different which is what I'm trying to compare.
Put the RB% you get at your current room I'm normally Silver star on stars when I play NL 10 so I get roughly 15% RB from Stellar rewards and FPP cash exchange bonus thingi.
Same routine for William Hill where average pot size below CAP and number of hands above and below CAP will be different as the CAP size is different.
So same way total rake is calculated payed by all players had those hands been played on William Hill and I get that I need 39.74% RB at William Hill atleast.
If you expect to get a certain amount of RB fromm room 2 then you can also calculate roughly how much absolute increase in win rate is needed in Room 2, so I assumed if I get 20% RB on room 2 then I'll need an increase in 16.44bb/100 in William Hill to make up for extra rake paid.
Maybe I took a bad example cause at NL 10 rake at William Hill seems very high but as you go higher in limits the difference should decrease.
This can also work for fixed limit or other type of games too, at fixed limit just be careful you convert everything to bb and not BB.
EDIT: I made a mistake in calculating increase in win rate needed, forgot to divide it by number of players at the table as that total difference in rake would be shared by all the players on a table. This is just a rough estimation of increase in win rate needed as not all players will pay equal amount of rake. Fixed it now, so in my example incrase in winrate needed would be 2.74 bb/100.
EDIT2: When filtering for pots below CAP also add another filter where hands saw flop since rake is charged only if a flop was seen. Should refine the results further.