I posted a couple of weeks ago that I would level an i25 blaster to compare the 2 AT's. Did that, and here's my take:
Both AT's will melt mobs, but the Blaster is clearly doing more damage.
The Sentinel is a much smoother leveling experience. Better thought out powers is both a pro and a con - easy to put the toon together, harder to min/max.
The Blaster really comes into it's own as an incarnate. Once fully IO'd, it loses a lot of the squishiness. But mez is always going to happen, though T3 Clarion largely removes the problem.
Sentinel clearly wins on leveling, Blaster gets the edge with a fully IO'd build. That said, there is a bit of playstyle preference. If damage/arrest rate is your primary fun, blaster. If feeling like an invulnerable arresting machine is your preference, Sentinel.
<I used Fire/Rad for the Sentinel, Ice/Time for the Blaster. Not one-to-one, but I'm playing for fun, not to further global science. Sue me ;) >