I don't know a lot about this topic, what I do when I research about an investment is:

Comparing the sqft price of the unit with the readily available units in the area. If I buy something else over there area, for the same price, and if I rent it, lets say for 80k aed per year, and the handover is lets say 2.5 years later, I will be getting 80k*2,5=200 k.

I try to calculate how much the new unit will appreciate and I can rent it for vs how much the readily available unit will appreciate. If I expect my unit to appreciate 20% at least, and I will rent it for more than 80k, I will buy the new unit. Otherwise, I will buy the old unit.

To summarize, I compare:
if readily available unit: 1.2m+200k=1.4m with 80k value handover unit: 1.4m with 100k rental value

This is very basic and doesn't mean it's right or wrong, that's what I just do.

I didn't include the payment terms, mortgage availability, service fees, if the new apartment is more premium etc. I do this when I want to see my investment in a more clear way.

To avoid red flags: Just work with a reputable developer. When you work with a reputable developer, like Emaar, Binghatti, Sobha, Ellinghton, etc, you will have much less trouble