Interesting. Never used FStop bags.
But since someone posted Lowepro. I have their larger backpack and regret not getting wheels. For any bag I get now, unless going very light (only body and a couple lenses) I will get a wheeled bag.
Oddly LowePro has ZERO messenger style bags.
The "messenger" bag is my favorite design as it gives me direct access without sling or putting anything down.
So there is an old Tamrac that is a bit on the large side that is messenger and with rollers. I love it, but need a bit smaller with rollers and messenger.
I wish I was a bag designer!!! :-) If think many folks have a bag in mind specific to their needs.
I tried to find this magic bag, and now have maybe 15 bags....Out of all I use the VanGuard Uprise38(ne rollers, compact) the most, and the old Tamrac with rollers for more gear needs.
In the years that I have had a backpack style bad, even for tekking, I have only used the LowePro large backpack as storage, and Never carry it as a backpack with gear.
I've realized backpack style bags do NOT work for me.