If cost and space are not an issue, the 40/40 is the way to go.

On the financial issue, it is possible likely that the 30/40 panel equipped with breakers for the 40 circuits could cost more total than will the 40/40 with breakers for 40 circuits. I have not done the calculations. The tandem breakers are higher cost. And I find higher failure rates of the tandem breakers.

Darrel, I was FAR from rude or snippy. You're just over sensitive because I called you out on your advertising.

I don't know where you or the OP are shopping, but a 40/40 200A main breaker panel is milk and butter in pretty much every area I can think of. It is HARDLY a "special order" item. And in many places it is the same or even sometimes less for them as opposed to a 30/40 because they sell so many more 40/40's.

Maybe you are talking about a home center? Even though many folks think if a home center doesn't stock something it is rare. That is not even remotely the case.
My local supply houses have piles of 40/40 panels in many varieties.

And thank you Dennis.

I found the 40/40 QO panel at a Lowes across town (normally carried, but no stock elsewhere). I think I'll be happy with the space and the price wasn't much more than the "combo deals" elsewhere. Thanks for the comments.

Dan