If I am not mistaken in the CO
timetable if you do a flight search the designators are something like this: 135/SRJ = ERJ135, 145/ERJ = ERJ145, ERX = ERJ145XR
However, I would assume there are instances on shorter hops where any of them can be substituted for one another...
I believe the interiors look the same...the safety cards are probably the same also. I had the pleasure of taking the 135 and 145 this summer DTW
and also the CLE
segment on the return and it had the same safety information cards on each aircraft... It was my first time on a regional jet and I really enjoyed it; its a little heavier on the turbulence (i guess i would assume not as heavy as a prop though; although I haven't ever been on a turboprop either).... I'll be taking my first ride on a CRJ in about a month and I'm looking forward to that also...