Most beginner missions from events give comparable exp to 2-1 farming, especially when you take the SG exp into account.

I've been leveling rather steadily lately as I'm probably the lowest level forumer, both on my main and my alt, and I've found that most of the time in the last 2 months, farming Current event beginner stages offer better TP raising due to the drops for those maps including Lvl. 5 Manyu and 1% affection gifts. The addition of Manyu to the pool makes the rewards over long periods of farming favour TP growth over your own Commander Exp Growth like 12-5 might favor, as well as cutting you off from getting Ampis. For higher level/higher TP players this makes these maps less favourable to run as you do not have a need for the lower level Manyu and the bonus exp offered over Expert maps is often not enough of a justification to cut out the 80 Stam SGs and Ampis.

However, tested in this most recent event, I've been comparing the worth of running the Phase 1 Current event map VS farming 2-1 in terms of efficiency, and I've had results that heavily lean towards Current Events (Important, as all Re-Issued event maps drop nothing but sealstones and thus remove these from grinding viability) being more efficient to farm for Exp/Gifts/Manyu/SG spawns than 2-1, which does cost 2 extra stamina (6 minutes) per run over the Phase 1 Beginner map.

The downside is 2 chests on our current map as opposed to 3 on 2-1. Bad RNG could lead you to getting those two chests containing nothing but 2 Star girls every run, however in my experience I've noticed that 70% of the time or more one of those two chests, if not both, contain either a gift of 1% value or a level 5 Manyu of random colour.