Alright, +1 flaming burst rapier vs +2 flaming rapier. Standard assumptions:
+1 flaming burst rapier
Noncrit: 8
Crit: 18
Total: 11
+2 flaming
Noncrit: 9
Crit: 14.5
Total: 10.65
So the rapier does show a slight increase with the burst property. However, its important to note that with the rapier our assumption is being really stretched. We are assuming that every roll of a 15 or better will actually be a critical threat. That's a lot more likely when you need 19's instead of 15's.
+1 flaming burst rapier
Noncrit: 8
Crit: 18
Total: 11
+2 flaming
Noncrit: 9
Crit: 14.5
Total: 10.65
So the rapier does show a slight increase with the burst property. However, its important to note that with the rapier our assumption is being really stretched. We are assuming that every roll of a 15 or better will actually be a critical threat. That's a lot more likely when you need 19's instead of 15's.