So I promised I'd follow up with our review of the Parkway SGL and here it is:
Nothing but positive things to say! DS likes the seat and seems comfortable in it. We'd borrowed a friends Recaro Vivo to try it out and after 40 minutes of riding in it DS said his back and bottom hurt. The seat base didn't seem deep enough and his thighs hung awkwardly off of it. I was worried that we'd run into the same problem with the SGL as it was only slightly deeper and had a narrower footprint, but this does not seem to be the case and the increased depth seems to be enough. The SGL is easy to carry and suspect for an HBB it will be easy to move from car to car. The features I like most are the Secure Guard to keep the belt positioned properly and that it latches (and easily!) The fitting for the Secure Guard is easy to use and after showing DS how to do it the first few times, he can now do it himself. I think it's a great idea and gives me piece of mind that his belt will be positioned correctly. I also think finding a seat that has latch is worth the extra $ as I can't imagine remembering or taking the time to belt the seat in whenever he wasn't riding in it. We have a Toyota Sienna and the SGL fits nicely in the seat. The head restraint is high but I am still able to see to the rear. Besides we needed the height because DS is tall. The head restraint adjusts super easily (can be done with one hand) so that the proper fit and shoulder belt position can be achieved. We bought the SGL in Cloudburst and the material is a nice quality that it typical of Britax. Looks like it will be cool in the summer and clean easily if an accident occurs.
So there it is, my glowing review of the SGL. All that being said, I still have a little doubt about whether we should have gotten the Monterey as I like the additional depth and shoulder width adjustment that it offers. It also has latch, but claims to prevent submarining by the angle of the seat base. While this might be true, I think the Secure Guard on the SGL made more sense for us as DS (age 7) is still learning how to use a HBB and buckle himself in. Perhaps if he were older I would have gone with the Monterey. As many have said on here, the best booster is the one that fits your child the best and positions the belt correctly!
Hope this helps someone out there with their booster shopping!
Momma to 2 ACTIVE DS
ETA: DS fell asleep in it for the first time yesterday. Obviously it was comfortable enough for him to fall asleep, but the headrest seemed to support his head comfortably so he wasn't in a weird position. Another reason I'm glad we went with a HBB!