Set or Top Pair?

[StringerB]

I have a general question - not sure if this is the right spot for it but...

Played a hand where 1st position opened for 8xBB. I reraised all-in with AA. He had KK. He hit a set and won the hand. That got me thinking about playing the hand differently. What if I had just called his raise and played the hand out?

Example - Playing .10/.25 Blinds. Villian has $25 stack. I have $25.

Villian opens for $2. Assuming I just call and the blinds fold, now I'm heads up. Pot is ~ $4.25.

Flop of K-9-4 Rainbow. He checks, I bet $3, he goes all in.

Do you call? Do you put him on AK? KQ? Or did he make a set? Only been playing at the table for a short time - have no read on villian. How would you decide between a set and top pair?

Thoughts? Suggestions?

Thanks in advance.