The main differences are UI, price, and quality.
The MT2A is on the budget side and good bang for the buck. I like the head loose/head tight two-state UI but the flashing modes are NOT hidden.
Cycling through with a single forward clicky can easily mean jumping onto the next level and the mode memory means cycling through the flashing modes. The low output is also too bright. I have seen several reports of beam artifacts but this is not a big deal.
The LD22 has a higher price but no doubt better build quality and in some respects a better UI. I don't dig electronic side mode switches at all but if you don't mind them the LD22 offers hidden flashing modes, mode memory, and an acceptable low brightness level! The LD22 is also available with XP-G2 while I think Nitecore are still fitting the older XP-G on their MT series.
I'd say make your choice based on the UI and runtimes. I wouldn't bother about the lumens as any difference is negliegeble if perceivable at all.
Hope that helps!
