Stereo RELs, two different sizes?

I’m running a pair of REL subs but they’re not the same model. One is the S/510 the other is the T/9i. I have them positioned so they’re opposite to each other meaning the larger S/510 is in the right front corner. The other smaller T/9i is just to the left of the listening position. I have them pretty well dialed in regarding the level and crossovers for each. Sounds great! My question is what I might expect to hear if I was to replace the T/9i with another S/510 so the subs are the same size/model? It’s sounds amazing as is but had always intended on getting another 510 because that makes more sense to my brain but it sounds great as is so why bother? Probably just answered my own question but I’ll hit post anyways. Thanks!