Small/ mid size venues

These are all UK venues but what is the perfect small venue capacity?

Liverpool Royal Court 1,186
Nottingham Rock City 2000
Cambridge Corn Exchange 1,738
Kilburn National Ballroom 1,913
Royal Festival Hall 2,700
Royal Albert Hall 5,544
Hammersmith Apollo 5,039
Wembley Arena 12500 (would have been 10000, pre 2006)
O2 arena 20000
Garage 600
Barfly 200

Saw them the first night of the Dream Tour at La Riviera, a 2400 people venue, and it was amazing. They played two nights in Madrid. They should do such a tour again. I don’t care about the visuals, the lighting, the riggings, the infrastructures, the large complex shows, the damn Jason click track in every song. I just care of five guys giving us a bunch of great songs on a stage. Only the sound matters for me. There are plenty of 2500/5000 capacity venues across the world to do such a tour.

yes small venues with the biggest names is always a dream, i like to see them at oslo opera house, thats a real small venue with fantastic accustics

In 1996 I saw them at GMU in Virginia, which is listed as 2k seats. It's so long ago that my memory isn't clear what it felt like and I think it was approximately my third show. It was small enough that Robert came down into the audience and sang Close to Me to a girl in the audience. He also called Mary from the stage to have us sing her Happy Birthday. So, it must have been fairly small. 

Reflections NYC was at the Beacon which has a capacity of <3k. Having primarily seen them in arenas save a couple of amphitheater/outdoor shows, that definitely felt small. Not great acoustics there, though. 

My bet is it will primarily stay large venues with a smattering of smaller shows throughout, as for a while. As others have said, I don't care about the smoke and mirrors, as long as they sound great.