IMHO, the best trainer depends on what you intend to do with your training, and how much money you have available.
If your ultimate goal is to be an R44 or R66 owner and/or operator, either commercially or only for private use, then obviously you want all of the Robinson time you can get.
Of course, there are many on this forum who would say that any aspirations to be a Robinson owner/operator are foolish, and if that is all you can afford you should just give up your dreams of helicopter flying right now and limit yourself to watching Youtube videos, because Robinsons are far too dangerous to fly
I do not count myself among them.
If your intent is to, somehow, transition directly into more expensive equipment, particularly Airbus models, and if you can afford the rental rates, the G2 may be a better option.
However...Robinsons still well outnumber the Cabris. Very few people are in a position to "transition directly into more expensive equipment". If you take the classical civilian path to helicopter glory, i.e. student > commercial > CFI > hour building as CFI > and so on, then you will have a much better chance of obtaining CFI/hour building positions in Robinson helicopters. In which case, again, you are going to want as many hours in Robinsons as possible.
Being US based where there are only a handful of Cabris, S300s and the like, obviously one tends to be forced to go with Robinson. I did have the opportunity to fly a Cabri for a couple of hours. FWIW, I liked it less than the R22 with three exceptions: it's plush, low-g pushovers are fun, and auto's are trivial compared to the R22. That last point is an important one. If I was a newly minted G2 pilot and had to transition to R22s for a CFI position, R22 auto's would no doubt come as a shock to the system. The reverse situation, i.e. being able to auto an R22, probably makes everything else seem easy.