I think I know what you mean.
You can lookup the dimensions but aircraft with similiar dimensions have very different feels to their interiors.
I can tell you this I have flown the Mooney, DA40, DA42, Commander, Aztruk, Seneca and some of the Beech to think of a few. The thing I like about the Cirrus is the aircraft feels big and roomy. The dimensions from memory are very similiar for example to the 42 but the cockpit feels a great deal roomier. It is smaller than the Aztruk but feels comparable.
In short I always say they must have been built for big fat Americans and I think they have the interior spot on. It feels roomy, very comfortable, a pleasant seating position and generally works very well. You would need an Aztruk to get close, which would be a great cockpit and a little roomier but sadly is rather dated these days.
Of all the singles I have flown I would genuinely have to say in my opinion it is the best - few come close if you take in the round all the things it does well. There are singles that are better in some respects but fall short across the spectrum.