Ok, here it goes:
For all of them you can slide out and lock and simply transfer the internal/external measure to the working piece. When I work fast on site I usually don't even read the scales, I just transfer point blank.
The Red One: 6.1M, built in clip. Chunky and sturdy. Red scale for internal measure/tongue out. Black scale for normal / marking point. Learning curve on this is short and steep: once you've made a few ten cm (100mm) pieces too short by reading off the red instead of black you won't do it again, even if tired. :-[
Pros: Length and sturdiness, tape lock is very secure. Cons: a bit bulky for the finer work and perhaps too big for pockets.
The Black One: 3.1M, no clip. Opposite side scales Red/Black same as the Red one. Sturdy tape. This model is the one I use for most work, it is sturdy and reliable.
Pros: Good length, sturdy. Lock is very secure so when you fit stuff you can poke things in place with it. Cons: this model seems to snag a bit around 1.6m and then eases off again. No clip.
The Blue one: 3.1M, no clip. Opposite scale reads radius. (strap the tape around the object and read off the radius scale). Red and black (int/ext) measure markings on same side, not as easy to mix up.
Pros: Best length/size ratio. Smooth action. Cons: no clip. Tape not as sturdy as the Black TMS, but it works fine up to around 2M, can sag if not supported by material or if you flick it slightly when it is extended between 2 and 3M.
The Green one: 2.1M, no clip. (Mine has been fitted with one though you do this at the risk of ruining the return spring). Ext/int measure on same side, radius on the other.
Pros: smallest of the lot, smooth action. Oh, and it goes well with the Festool green. ;D Cons; 2.1M just a bit short at times.
My recommendation goes to the Blue one for shop work and the Black one for on site work. The Red one for bigger stuff, obviously, and the Green one for the missus.
I could not decide so I got the lot; two of them I got as a gift and I bought the other two. I use the Black one on a daily basis and the red one on bigger stuff. The blue one is not seeing much use but that is just because I preferred the black one for my filthy lucre work. The green one is in the sowing box. Go figure.
For extra tight work I slide out, lock and then add a half or a full mm when doing internal fittings, depending on what type of saw I use. This gives a real tight fit.
