That's a good and hard question tbh.
Season 4 as a whole is great and my fourth favorite season of the entire show. I don't think 4a is that better then 4b, I think they both are amazing and 4b is not that weak compared to 4a.
But, I think that 4a is really amazing but not like 1-3. Yes, the episodes are great and the jokes are funny and hilarious but it's not the same for me.
I think that season 4 is closer to season 5 then to season 3 in terms of quality(season 4 is better then 5).
So it's pretty hard because season 4/4a is great and close to 1-3 but not close enoug for me to consider it as a Golden Era season. It's more like a silver era alonge with season 5.