To add onto this:
If you have room in your HUD, then RFI by position seems to convey a lot of information at once. Besides the raw stats, you can see how positionally aware a player is.
Personally I think you should always be able to make room for the RFI stats, as they're just incredibly useful. Not only do they give you an idea of a player's approximate opening range, they also show you if a player is positionally aware or not.
Also, let's say you're playing for example a 11/9 guy. Of course this player is a super nit. But when you look at just VPIP/PFR (or total RFI and coldcall, whichever you use), you'll expect him to be just that: a nit.
But it's certainly possible that this guy will open up to 50% or whatever on the button, which you probably won't account for unless you use popups a ton. And I'd imagine most people don't really use the popups often enough. Also, you might expect a 20/18 player to be fairly decent. But if he opens 18% or so from all positions, clearly he's not positionally aware and clearly isn't one of the better players around.
Again, if you have to use popups, you are pretty likely to miss this information a lot of the time, as you're not going to use a popup every time somebody open raises. And if you do, then it costs you a lot of time and you might as well put them straight on your HUD.
RFI for every position is the nuts to have on your HUD imo.
edit: I also still like to keep VPIP/PFR on there, not sure about switching them with total RFI/cold call.