Assuming it's a serious question, quite a few things
Up until not too long ago, there were three airlines within one airline
- 145s - legacy Eagle I guess in many ways. A regional, or commuter, whatever you want to call it. Out of DFW you can fly an entire 4 day without ever leaving the state. In ORD that's harder, but most flying is bouncing around the lakes. NYC and MIA had longer routes, but both are gone now. Doesn't make the flying unimportant or lame, mind you, just more "classic regional".
- CRJ-700 - the "Original Eagle Heavy". Word has it, back in the day the CRJ guys and 145 guys didn't even talk to each other. Might be an exaggeration, but the spirit was proud (mainly meant a schoolhouse that was ran like a tight ship and always going everywhere fast - ask
@NovemberEcho). Again, back in the day the pay between the fleets was very different, the flying was different (generally longer routes, no 6 leg days etc). As of 2 years ago the CRJ is gone, just about everyone moved over to the 175 (schoolhouse people included, which resulted in tightening the training, which is nice from my perspective).
- 175 from the get go was set up as a completely different program. You could almost still read "US Airways" on the top of the training manuals. From checklist usage to callouts to general training attitude - different airline. Longer routes from the get go, which translates into more efficient schedules (no sits in between 6 legs to the max FDP day type crap), new (at the time) airplanes, more modern avionics and automation etc.
Tl;dr practical application -
Longer routes. 3-2-2-1 4-days vs 5-4-4-3, typically more days off per month as a result of a more efficient schedule.
Flying in the open time, consequently, more likely to yield better OT - BZN turn is 7.5 hrs and takes, say, 9 hrs from sign in to see ya, ORD-GRB-ORD-GRR-ORD blocks probably 5ish and will take 8.5 or so hrs to do.
General office set up - dual fms with vnav and autothrottles > single universal box and 3-to-1 rule.
Newer airplanes > old airplanes in terms of flying around with MELs
The flip side - I've never flown a 145, so have no opinion there. Heard it's a POS from an Embraer company pilot I used to fly charter with and every singe CRJ guy that did a short stint on it when displaced into the left seat (was a thing for a while).
Guys flying it say good things about it and send me memes like this one -
View attachment 63116
Also, it is generally a junior airplane in terms of seniority - so less wait for a line/weekends off/etc.