100% agree, the M5, rocket like downhill and in a straight line was too much hard work on twisty stuff and in traffic. There's no way I could have toured it like the Cruzbike.
Was it the "aggressive" recline and bar setup, the chain/heel/wheel interface or both? It's interesting to compare views on this, as this guy went from Cruzbike to CHR
https://recumbent-cyclist.com/bikes/m5-carbon-high-racer/
(I know you didn't have the CHR but I thought you had the highracer - could be wrong of course)
M5 M-Racer in my case, same design as CHR but Cr-Mo. I'm not the tallest of riders, so with that reclined seat I needed a 26" front wheel to have a decent view of the road. I solved the chain/wheel interface by having a high idler set up in the head tube area with a home-made chain guard to stop it eating the inside of my thigh.
The heel/wheel interface was still occaisionally a problem.
Cruzbike S40 by contrast, 2 x 700C wheels, conventional length chain, all out of the way. The front end is the rear end.
S40 vs M5
Looking over your shoulder is possible on the S40
Low speed handling is easier on the S40
Absolute speed probably a bit lower on the flat, M5 untouchable downhill
S40 - with a triple up front is like a triple on a road bike, in terms of chainring/cassette combinations. With the long chain on the M5, if being lazy you could use 2 x 11 fully
TRaction in the wet, uphill can be an issue on the S40 as the front wheel is not heavily laden
The S40 is more of a fast tourer than a racer, for a more even comparison I'd compare V20 and M5 (the number is the seat angle)