Well, Im done lurking at all the post and about to get my first trike. I am aiming at getting catrike expedition (2nd choice) or the Road. I really like the air shock suspension because I will be riding on roads in Iowa that have more cracks than moms vase I broke years ago. Has anyone seen a road with the 26" rear tire? The bike shop I am dealing with is special ordering my color along with the kit to make this possable. (with no obligation to buy). so when are weather finally gets out of the winter stage, I will be test riding the normal Road, the Road with the 26" tire and the expedition.
I know that it will gain me a little more hight, Im guessing around 2" where I sit. will this mess me up in any way? Also, I have a Tail wagon that my two (small) dogs ride in. will this cause me problems? The main question I have with this is the air shock, will it mess me up pulling a wagon?
If anyone can give me some insight on what to watch for, I would really appreciate it.

I rode RAGBRAI one year on my Baron; and was on quite a few of those concrete roads you mention. The kind that have such wide cracks running down the center line that I was afraid to do left turns. I didn't have an issue with cracks running across the road, even though I had no suspension.

I ride a Road and really have no issues with most cracks in the asphalt. I have seen situations where having a suspension would be enviable, particularly where paved surfaces end. As to the 20/26", there are quite a few threads lurking about that subject. To condense more than slightly, the 20" wheel will reduce average speed/gear inches making it easier to pedal (in general) but harder to obtain higher average speeds. The 26" wheel increases average speed/gear inches. I have read that the flex in a 26 is more noticable, and of course you have to consider only needing one tire and tube size.
I have not had any issues with ground clearance on my 20" Road and appreciate the wheel size when going up hills. The area I moved to is very "textured" and in addition to the small wheel I opted for a SRAM DD3 to further increase my gear inch range.