I guess I'm approaching this with the idea that someone is starting new right now. Having had to previously buy and redeem your exports is in my opinion not that easy to do if you haven't already done it--it's literally impossible if you haven't already done it. At least on 360 you can just buy the old discs to play those songs. Beatles is actually completely delisted for example and doesn't carry over to current gen, all that DLC is gone too.
No adapters are needed... if you already have them? You do need special MIDI adapters to hook up real drums to PS4/5 if I recall correctly, which are so expensive that they are being custom made by fans.
For someone starting out right now I think 360 makes the most sense... just my opinion though. Other platforms lock you out of the songs you most likely remember from back in the day, if you haven't already redeemed DLC/imports from old gens. And to be honest, the RB4 track list kinda sucks compared to any of RB1, 2, or 3.
I do appreciate you chiming in however, I am still learning about all this.
I'll hit each point.
Yes, none of the exports are available at this point. There are
some songs from those exports that Harmonix made available as DLC for RB4 (a list is in my OT that someone linked towards the end of the previous page), but yes, if you want to play, say, Green Grass and High Tides or Panic Attack, you would need to play them in their respective games if you did not redeem your export codes before they expired 5 years ago.
There's a difference between adapters and dongles. PS3 instruments required a wireless dongle that came with the instrument to connect to the PS3, whereas 360 instruments were able to connect directly to a 360. To use a PS3 instrument on PS4/5, you just need that dongle, no adapters of any kind. The lone exception of course is if you wanted to use a real ekit, which requires the midi pro adapter, which you would have needed to use on a PS3 as well. To use 360 instruments on an Xbox One/Series, you need a wireless legacy adapter in order to allow you instruments to connect to the system.
As for where to start, that's going to be based on preference. If you have any intention of moving forward, PS3 is probably going to be best bet because it's much easier to take your instruments, arguably the most difficult piece of this puzzle, forward because you'll already have everything you need to use them in RB4.
