I'm a big fan of Guitar Rig. I have used amplitube in the past, but not the other two. IMHO, If you're not happy with Guitar Rig, you won't be happy with a simulator. Period.
I'm a long time PodXT Pro User. But now i ended up with the creamware dynatube plugin. 4 simulated amps with cabs for recording/reamping: Vox AC30, Fender Twin Reverb, Marshall JCM800, Mesa Boogie Rectifier.
this plug works only if you have a creamware dsp card (sharc dsp's) in your computer. but the plug has the best simulation i've ever heard. technologie is from http://www.softube.se
As we talk for DSP i like also NIGEL from the UAD-1 DSP card...
If you are using pro tools there's also great stuff from line6...
I've read and i believe that Gring is the best of the plugs you wrote before...
I've been trying different guitar amp dsp's, plug-ins, sans-amps, etc... for years. I've tried most of the ones you listed, just got UAD-1 and like it lots, but I think you should also add the Izotope Trash plug-in - it's useful as well.
I've used line 6 gear since it was first introduced. Being very used to it, how to use it, etcc... it's the first thing I reach for.
With all that said I've been a professional monitor engineer for 6 years and have worked with a lot of national acts. The majority of them have some form of Line-6 stuff in their racks or on the floor - From Puddle of Mudd to Jonny Lang to Stanley Clark, and a lot in between. I can also tell you from first-hand knowledge that many of the hollywood studios churning out soundtracks and records are using the Line 6 Variax guitars now as well as the amp DSP's. Why? Quick and easy, and really, the average schmuck listening doesn't know a Fender Champ from a Marshall Plexi or a 57 Strat from a Paul Reed Smith.
Forget the knobs, names, image - does it sound like you were hoping it to and does that tone feel right for the piece. The quicker you can get that, the more time you have to play music.
PS - don't forget the tonal influence of the entire sound chain - software, sound cards, listening amps and speakers, listening room, on and on and on and .... then the mastering engineer comes in and changes the tone anyway.