Actually "most" RIP's internally use APPE or CPSI which are actually Adobe's print engines (Adobe PDF Print Engine and Adobe Configurable Post Script Interpreter) and the rips actually work best with Adobe RGB profile files. sRGB is not bad (CMYK is far worse) but Adobe RGB will give the widest gamut. Not sure on what the actual RIP engine is in VW but it is Adobe in FlexiSign. Also as mentioned - an i1 and making your own profiles give the best results. Part of the problem with pre-made print profiles is those are optimized for someone elses printer in the environment that printer is normally in. Average temperatures/humidity, and the individual machine play a big role in color.
Personally I use Adobe RGB but I also have a monitor that can render the Adobe RGB color space. Many monitors can't so in effect if you're using Adobe RGB on a monitor that can't render the full Adobe RGB you're basically working blind with some colors hence the suggestion to use sRGB just to be on the safe side.
Totally agree that making your own profiles is the way to go.
Here's something that trips up a lot of folks trying to get a grip on a color work flow. Intuition would suggest that a red defined by R255 G0 B0 would be as red as it gets - not necessarily so though. On our set-up that gives a somewhat washed out reddish orange - R222 G0 B0 gives a nice deep red and I get a nice fire red using R225 G38 B28. Counter-intuitive no?
Something else that confuses many is that intuition would dictate that CMYK would be the way to go because the brand new shiny wide format digital printer sitting on the floor uses CMYK ink. Easy to get confused by that but the thing to remember is that it's the RIP that's doing all the heavy lifting when it comes to determining how much of each of the CMYK ink to lay down in order to get a nice red.
Basically, linearize the printer, build your own profiles (you'll need an eye1 or something similar), design in an RGB color space and trust your RIP to do what it was designed to do.
Dan
