Trane s8x1 vs s8b1

I am replacing 2 HVAC systems. My house used to be a duplex is why I have two. I am going with the S8B1 since the install will cost $2000 less then another company quoted for the S8X1. I don't think the X1 would save us 2k over is lifespan vs th B1. But I would appreciate any 2nd opinions.

Also, shout out to jbfan for responding to my request for a recommendation with this company. Great price and great reviews.