Feel like I can update this a bit more accurately as the last few days I've been using various cutters.
Was working with another tiler yesterday and he produced a TS50 Plus out of his van. Decided that I'd give it an open mind and use his cutter to see how I found it. Both working in a large bathroom together. Seen the appeal of it and found it easy enough to use but it had a few problems. It seemed to struggle to cut 10mm off a
tile. Wasn't sure if it was just me but the fella I was working with had to use the nippers for it too, the Rubi just didn't seem to want to break them cleanly. The other main downfall was that if you were cutting a U shape check, on the sigma you'd scribe the back line, run the other two lines up the wetsaw, and then put the check back on the cutter and break the handle above the scribe to remove the centre piece. Didn't seem to be an option to remove the centre piece on the Rubi because the breaker was fixed to the top - no use if you want to make a break elsewhere on the
tile. A decent machine but definately wouldn't have rated it as highly as the sigma. The other tiler who'd swore by Rubi for years even seemed to have a bit of difficulty on stuff where the Sigma wouldn't have had any trouble. Not sure if it was a lower spec cutter or if his just wasn't well serviced so wouldn't base my whole Rubi experience on that one day. Wouldn't snub my nose up at a TS50+ but definately over rated for what it was, in my opinion of course.
Then today, was working with 120x60 porcelain and needed to borrow a cutter which would take the size. Borrowed a Sigma which was the height of me, however this was a Klick Klock style handle which I'd never used before. It was a very capable cutter and had a very good quality feel to it. The klick klock system worked much better than the conventional pull handle breaker would have done in the situation. Thought it would have been a gimmick but it definately gave you more breaking pressure than any other style of cutter I've used. Rated it highly but would only use the Klick Klock system for very heavy/strong tiles, felt it would be rather slow and tedious if you were using it as an every day method.
Overall, still reckon the Sigma pull series have it in the bag. Yet to use a Montolit cutters so shall reserve my judgement on them until the time. From talking to the other tiler about the price of the Rubi gear, the Sigma's seemed considerably cheaper too.