Hi Joe,
Unfortunately, it's difficult to compare the two planes because they are really very different.
Assuming 'apples to apples' comparisons (as much as possible) the Sonex should ultimately be a lot cheaper to build, primarily because of the engine cost. It will also be a lot cheaper to operate in terms of direct operating costs. It *should* build a lot faster, due to pulled-rivet construction. It might well be cheaper to hangar, it carries less payload, it's slower, it's unlikely you can do acro in it safely if you have a passenger larger than a small child, etc. It *can* qualify for light sport operation, if that is or will be a factor for you.
Bottom line: the -7 is a lot more airplane, for a lot more money.
Charlie