Probably of little help today but for all our long haul touring trips in the noughties like Africa, India, Peru and China
We used G Adventures or as it was known then Gap Adventures
Back then I thought they were great, offered a good all round package that I couldn't really fault
The food, the restaurants, the accommodation, transport and guides were all of a very good standard
The size of the groups varied on each holiday from us and another couple to a group of about a dozen people at most
And every one of those holidays ran like clock work so much so that we were delighted to find out that our up coming touring part of our holiday trip to China and Japan is with G Adventures
I can only presume that the other 3 you've listed will be of the same standard so I'd be of the opinion to pick the tour that ticks all of the boxes you're looking for in this type of holiday
One bit of advise I would give though, and I'm not sure if you're doing this or not, is to use a travel agent like Tropical Sky or whoever you choose rather then trying to book everything yourself for two reasons
1. The price, we've found over the years that there generally is very little in pricing between the two options, if you end up paying more it's usually only a couple of hundred euros but sometimes it can be considerably cheaper as the travel agent can sometimes access better deals
Like this years trip to Japan, I think we have saved a few thousand compared to when we priced it last year doing flights and tours separately
2. If something was to go wrong on the trip, you've only one phone call to make and they, your travel agent should sort everything out for you
I was in the middle of nowhere in China near the 3 gorges damn when I got a phone call to return home for a family emergency
And it really was one phone call and everything was looked after from the internal Chinese flights to Beijing, Accommodation in Beijing, to the next available flight home they did everything for me and kept me informed of everything along the way
Another bit of advise I'd give is get a
credit card that comes with travel insurance and book the holiday with it so as you don't have to worry about any of that area at all