RR has built a good family of engines, especially after killing themselves with the original RB
-211. I have to say I got a bad taste for Pratt after dealing with the results of several "events" on the PW2000 series. I am more familiar with GE
than anything else though.
The interesting thing about the CF6 series and now the CF34 series is that the most recent versions are completely different from the original versions. The CF6-50 has a modified core and a new low pressure system when compared to the CF6-6. Going from the CF6-50 to the -80 GE
then replaced the core. This means that the CF6-80 shares almost nothing other than the name with the CF6-6. The most recent models of CF34 have done the same, going to a CFM56 based core. In my biased opinion GE
does a great, maybe the best, job of "sweeping water uphill," hence the high OPRs, 42:1 for the GE90, and 43.5:1 for the GP7000, which they share with Pratt, GE
does the core/high pressure section.