The base M3 MBP isn't a true MBP. It's to replace the 13" MBP w/ touchbar, which was always a lower-end black sheep of the MBP family. Now that they've removed the touchbar, they've consolidated it into the regular MBP lineup, but it remains crippled.
If you were considering a 14" or 16" M2 Pro MBP, the equivalent M3 Pro MBP would not be the base model, and WOULD be an upgrade... just avoid the base M3 (non-Pro) config.
If you were considering the M2 MBP w/ touch bar, then the base M3 MBP is the equivalent chip.
On the other hand, if you don't need the GPU improvements, or the mild CPU speed bump, that M3 gives and you can find an M2 Pro cheaper because they're "old", go for that.
edit: Adding "Pro" to M2 and M3 to indicate which were the proper MBPs.