FLIR and Wescam have the lions share of airborn kit.
Axsys has offered highest quality HD images but haven't yet developed the reputation for thermal imaging and integration compared to the others.
Gimbals less than 10 inch in diameter have become more useful due to miniaturisaton of payloads.
In the past 12 months more players entering the field of lower cost lower performance stabilised platforms.
On the other hand for extra special missions, you can have extra special payloads.
Mickjoebill