As others have stated, test ryde both
For me, the Spyder was my first motorized byke ever, and with cheufferring Teddy around, I wanted it to be as easy & less complicated to ryde as possible. I also knew we were going to get a camper & I didn't like the thought of being on an incline with a camper & dealing with the clutch issue. All my other vehicles in the past have been manuals & since we live in an urban area, with much stop & go traffic, well, that kinda made it a no-brainer for us.
I've never ridden an SM5 myself & I honestly don't know any benifit to it, besides being able to coast while moving (better fuel economy) & personal choice. The choice is yours & many of the posts you get here (like mine) are going to be biased. If its for your wife, make sure she rydes both.
For me personally, the SE5 was easy to get used to & it works very smoothly & you still have control. I think many SM5 fans think you lose control of shifting, but that isn't so. You have to up-shift every gear(thumb shifter, just no clutch) and the auto part only kicks in, if you choose NOT to downshift on deceleration. If you don't down-shift by a certain RPM (I think around 3200) then it will downshift by itself. The only other caveat, is that it will not allow you to UP-Shift if your not at a high enough engine speed, or RPM, usually around 3600 I believe. Many SE5 ryders find it very spirited to shift above 5000 RPMs, but the higher your shift points, the lower your fuel economy. I personally have found that Bob Denmans short-shifting pattern at 4000 or under works well, and helps increase your fuel economy, albeit a more casual ryding experience. When I was shifting around 5000 RPMs we were averaging around 24-27 MPGs, but with short-shifting around 4000 RPMs, we've gone up to 28-30 MPGs.
Whichever you choose, You've found the BEST place on the WWW for anything Spyder Related. Welcome to the Spyder-Hood.