The only thing to recommend against a bass reflex configuration is that a badly designed unit will tend to be boomy or muddy, which doesn't stop the low-rent builders from trying, as the increased bass efficiency reduces the box size and power requirements.
That said, I would also prefer the TSI300. Two 5.25 inch drivers have much more surface area than a single 6.5 incher (almost as much as an 8 inch driver, actually). The midbass response should be better, and the reduced bass efficiency of the sealed box is mitigated by the higher rated efficiency of the system and the broader frequency response if offers. 35Hz on the low end rolloff should allow these to blend very nicely with the subwoofer, and you may find the subwoofer crossover can be set as low as 40-45Hz.
He who laughs last, laughs first next time.