Hello,
I do think that room size should also be a factor in your decision. Unfortunately, you have not included this in your post. As has been noted above, you cannot lose in your decision. Hopefully, you will have the opportunity to listen to both speakers side by side. Or dream of dreams, in an in home audition.
The Spire certainly benefits from the upgrades gleaned from the CLX development in regards to the ESL panel. While many here prefer Spire+Descent over Summit, oftentimes sub integration can be difficult at best. Whereas the more capable bass section of the Summit is completely integrated with the ESL panel.
ML