You don’t have to choose. Nor do you have to use Topeak racks. Topeak is making an
add-on called the Omani Quicktrack adapter for their bag system. It bolts onto other racks so you can use the Topeak bag on just about any rack. I’m not a fan of Topeak’s racks because they use flat metal upper stays. They work but they aren’t very adjustable. Tubus Racktime and Tubus racks have round stays that have more adjustment ability with less fuss.
I use a Racktime bag and have for about 15 to 20 years. It’s a very good bag but I also have Tubus racks which won’t work with the AddIt system. My solution was to use an
Ortlieb trunk bag adapter on the rack and a
basket adapter on the bag. It took a bit more work initially and the Ortlieb rack adapter isn’t cheap but it works extremely well. I even use on for my micropanniers on my bikepacking bike
Untitled by
Stuart Black, on Flickr
Untitled by
Stuart Black, on Flickr
Untitled by
Stuart Black, on Flickr
Untitled by
Stuart Black, on Flickr
Topeak hasn’t made their adapter until just now. If I had to do it again, I’d use their adapter since it is a little cheaper and their bags already have the fittings.