The cotton inner was an option in the 80s (my dad's Plus model has one) that added a little extra weight.  I don't think it's available any more, but check with Saunders.  My Spacepacker is merely 10 years old (replaced one lost in a burglary of a similar age) but has the synthetic inner, and I can't say I've found condensation on the inner a problem.

Opening fully on two sides it's a very easy tent to vent effectively.  I like mine very much, it's light enough (1.9 Kg) to take for one, but (just!) roomy enough for two.  The caveat for the tent is itr's not a good design for tall people.  Used 2 up about 5'10" is a sensible limit, though used solo you can sleep diagnonally and get a bit more.  Some people find limited face-space when lying down an issue, but it's never bothered me.

The main reason I'd suggest an Akto over the SP is it's 400g lighter and has enough room for 1.  If you ever want to add a second the SP has the extra room where the Akto doesn't, however.  The Akto's inner has more effective room thanks to the corner poles, but the Spacepacker has a great deal more porch space.

Pete.