Premiermiles vs altitude vs 90o? Which card serves best overall?

Hi anon, I find that Citi PM tends to have promotions that run only for existing cardholders, so you might want to hold on to the card. Also, Citi Miles has the largest range of transfer partners and hence are more valuable in my opinion. For Altitude and 90, they tend to be offering better deals for new-to-bank customers.

Edit: PM and Altitude both have lounge access, while 90 does not, but has smaller conversion blocks when transferring miles. Altitude also has 3mpd on online airfare and I think hotels too. PM has good hotel promos (7/10mpd) with Agoda/Expedia/Kaligo, but you need to do your maths to see if it is worth it. Use this as a guideline as to decide which card would serve you best. The rest of the perks of the various cards won't make or break the deal for me.