Just my observation: I loved my M380 and still do, but I had an opportunity to get a M405 at a reduced price. Being a longer range shooter, I jumped on it. It has significantly more authority than the M380. Later, I was able to try a recently disabled person's BD400. That BD400 using the same limbs, string, and arrows and a brace height that is the fastest for each bow, is 5'/sec faster than the M380 and appear the same speed as my very attenuated M405. However, the 400 has a wonderfully gentle feel. If a gentle, fast, smooth Excal is desired , at least try a BD400. With only a Dr Stirrup kit and a light, Flemish string, the BD400 is very fast, light, gentle, and as accurate as any Excal. If a person wants an additional Excal IOT heave a backup, the BD400 is a great choice for a primary Xbow.
What am I saying? After serious reflection on this self iniated thread, I have to admit, that I too, would have been willing to "upgrade" to a BD400 if I hadn't lucked into it thru someone who got it but couldn't use it due to physical limitations.
So, in actuality, I'm one of those "upgrade" people also.