While my general recommendation is to progress, but not prematurely (details) I suggest you do not complete World 11 at all, because:
- The increase in XP from W11 to W12 is marginal (usually doubles since World 7, but here it’s only 15% more)
- The coin increment is anyway marginal
- There are no hidden treasures in World 12 - at least, no one has found them yet, which means you lose out on a useful source of energy, gems, coins, upgrade material and crystals
- The new perks you unlock are not very useful - what we needed was for Power Tripper and Sustained Fire to be buffed, not to dilute the perk pool by introducing improved versions
However, one thing I’m not sure about is whether the rewards in Mystery Crates when playing Endless / Endless Boss / Dark Castle events match the highest level available (e.g. +190 Attack is what World 12 offers) or only the highest you have unlocked - so if you only get less than +190 Attack / +1250 Health / +120 Damage in those runs, progressing to World 12 would help you a little in those events.