Doug
I have owned a combo gun 12 over 222, I now own a drilling 12x12x30-06, with scope in claw mounts, and a double rifle drilling in 9,3x74Rx9,3x74Rx20ga, with scope in QD mounts.

I really like the concept of a "combination gun" and use them when ever there are overlapping seasons of fur and feathered game.
I can sum it up like this.

A Combination gun is a perfectly good single shot shotgun, and a perfectly good single shot rifle.

A Drilling is a perfectly good double bbled shotgun, and a perfectly good single shot rifle.

A double rifle drilling is a perfectly good double bbled rifle and a perfectly good single bbled shotgun.

While it seems I have stated the obivious, think about it for a while... and figure out which would be the best choice for the hunting you do.

Do you want a rifle "around" while shotgun hunting... Or do you want a shotgun "around" while rifle hunting, or do you just want the sleekest lightest "combo" to carry with you while "bumming" around in the woods.

I do feel that ANY combo/drilling should have a scope fitted in QD mounts.

In fact the last few grouse I shot with my drilling in Idaho were killed with the scope still on the gun, and in Texas the last 2 turkeys, the duck and the squirrel shot with the shotgun bbl of my double rifle drilling were killed with the scope still on the gun.

Having a shotgun and a rifle "on the same gun" is an awsome set up.

My wife hunts with her drilling a 12x12x30/06 most of the time as it is her favorite hunting gun.

They all are great hunting guns.