As for NASAMS it looks worse on paper than Buk.
I wont quickly make that decision tho. There are some advantages compared to Buk's.
-First it's Active radar homing, means it has no limits on target channel, thus it can engage multiple targets simultaneously.
-Second, it can take designations from practically any sources including NATO AEW's in more direct manner. Suppressing the AN/MPQ-64 sentinel that might be linked to it would be helpful. However As we see in the naval field, you dont need X-band or other band typically used for fire control radar to help designate target for active radar homing. It can work just fine with maybe P-18.
-Third the launch can be completely devoid of any radar emmission. You only know when it's already launched. It creates risk for Russian aircraft as it may fly into Ambush and too late to activate its countermeasures. The differences is that it can reach hgher altitude not normally reachable by MANPADS.
It's basically a giant Manpads with more performance. The inferior range compared to Buk is of a little concern than the ability to engage multiple targets simultaneously. That assumes AMRAAM is provided.. it can however contain AIM-9X Thus it will perform basically same as Ground based IRIS-T.
The best thing Russian can do would be use drones to bait the NASAMS..and then lay the pain with Kh-59's The weaknesses of the NASAMS is that at current shown configuration..it's not as mobile. Unless Ukrainian decided to go Australian way and put it on their MRAP's.