I would sit your child in them to see how they fit. The moterrey does not always fit well (shoulder belt wise) for children with narrow shoulders. I'm not sure how wide the diono is either, but I think the turbo is narrower than most boosters.
The only drawback to the Turbobooster is that the backless portion separates from the high back WAY too easily. You have to learn to hold both pieces and keep them at a right angle when transferring between cars. That could cause an issue during field trips if teachers or other parents are handling the booster. Undoubtedly all the other kids will just be in backless boosters (if anything) and the odds are someone somewhere will think they "broke" the car seat and just throw the backless portion in the car for your DD or else let her go without a booster entirely.
If you do go with the Graco, though, I'd probably suggest the Affix version so it can be LATCHed into the car when not in use.
A Britax Parkway SGL would be another good choice. It's lightweight like the Turbo but doesn't fall apart so easily.
I like the Monterey, but I wouldn't want to move it around between cars much. It's pretty bulky.
A Harmony booster might be a good choice, too. They are lightweight.
I would try to pick something off this list: http://www.iihs.org/research/topics/boosters/best_bets.aspx
~*~ Full time mom ~*~ Hobby Sheep Farmer ~*~ Child Passenger Safety Technician ~*~
Thank you Brigala, for you reply!
Now that you say it, I realize how heavy the Monterey would be to move around. And I had no idea about the Graco Turbobooster coming apart. I guess both of these would be quite inconvenient for my purposes...
So, back to square one. I like the idea of a Britax Parkway SGL - it would keep my DD in a high back booster longer, given it's upper limits. And lightweight (and not falling apart) is a big plus. Will it fit easily in my 2011 Honda Accord next to the Radian r120 (rear-facing, but eventually forward-facing)?