I have been using a large and heavy Butterfly wet grinder for dosa/idli batter grinding for the last 10 years. It has given me good and trouble-free service so far. But I have now realised that I dont have the time for elaborate cleaning rituals it forces me to do after each round of grinding. Also, the heavy drum and rollers mean that I feel tired after the cleanup. not a good feeling unless it comes after a good gym workout!
Two months ago I purchased a smaller, lighter and smarter grinder - the highly popular Ultra 1.25 litre model. I have been extremely happy with my purchase so far. The drum is light and easy to handle, the roller stones are set on a post that has a handy collar that allows you to lift up the assembly easily, and the locking bar on top can be folded away out of the way after the grinding is done, so you can easily clean the drum and rollers. Grinding efficiency is great too, but that could only be because the stones are new - after all my Butterfly machine has 10-year old stones.
All said, I am quite satisfied. Ultra is the most expensive of all table top grinders, but I think it is money well spent if you grind a lot of dosa/idli batter.