For crosscutting, I haven't come across anything that my 066 couldn't shred in no time flat. I've buried a 36" bar and come up 6-8" shy of making through a couple of oaks in the past 2 or 3 years. Saw hardly knew it was there. Like a hot knife through butter.
Don't know what you would need a bigger saw for unless you were milling, or had to drive a 5 foot bar on a regular basis. An 088 is't a great "user" saw, and an 090 even less so (old tech and heavy, but could pull a freight train). You take that kind of animal out for the big job, and bring out a smaller one to clean up. If/when I ever wear out my Super XL, I want an 044/046 for "clean-up"...an 036 would be okay. An 066 is fun for just so long.
Mark