haven't used a topeak trailer but have had a bob for approx 9-10 years
the weight dif between the topeak and the bob is only 650g
the bob yak weighs about the same as front and rear surly racks with carradice super c's fitted so no real dif there.
the bob trailer catches the wind/drags a lot less than two sets of panniers, it tows really well you often end up checking to see it's still there, it lets you know its there on the hills though with the extra drag from another wheel
been car free for about 8 years my bob has been used quite a bit, it has carried stupid amounts of shopping,plus loads of trips to the dump,
if you intend touring i'd take a spare bob skewer as i have had one break, apart from that its been a real workhorse
best bit is if you intend to travel to one place with your camping kit then go on day rides on a nice light bike not weighed down with racks n crap
i rarely ride my sherpa as with full touring kit (racks dynamo lights large bottle cages) it's not the best bike for daily use, if i ditched the racks n crap and used bob instead just when needed the bike would be usable on a daily basis, but it will stay set up as it is.
if you are ill while away bob can be a pain though as the trains don't much like bike trailers, where as racks n panniers are no problem
I prefer single wheel trailers as they track virtually in the same tyre track as your rear wheel, and are about the same width as your pedals, upshot is you ride like normal
parking needs a bit of thought , ride up close to a wall and lean bob against it and the bike stays upright, but if your on a slope you'll need a strap to keep one of the brakes on to stop it rolling
it was mentioned up thread about jackknifing only ever had it happen a couple of times and that was off road scrambling down steep slopes if you doing that on a regular basis then i'd unhitch bob and carry stuff down,
if bob had a drag brake it would be awesome
mmmmm i wonder new bob wheel with a drum brake? is that doable?
panniers or bob? i use both and at Christmas i used both together for the Lidl shop
sorry can't help about the topeak but can't imagine it would be much different to bob in use
ATB Bill