The two forms torque sensing and non sensing are like chalk and cheese on the trail, much less so on the road. The Bafung series were built to put on Chinese commuter bikes, the Chinese don't do exercise on the way to work, the Bafung therefore was designed as a pedal and go, push the pedals and the bike will ramp up the power until you reach the speed you want and hey presto you are at work without a sweat.
The TDSZ2 is a torque sensing beastie and if you don't put any energy in, it won't either. Simple, it makes you pedal harder and it will match you by a percentage depending on what mode you have it in, not unlike the Bosch and Yamaha versions.
On the trail the BB series are a pain in some ways, you have to be prepared to program it to your requirements, from the factory they are terrible off road. But there are plenty of programs available and they program pretty easily and you can get them sort of good particularly if you have some sort of impediment such as a damaged knee or fitness problems. I have mine now where its comfortable off road but more like a small motorbike than a pedal bike. They also require quite a lot more hardware on the bike such as brake cutoffs as they can be somewhat slow in shutting power down on single track style riding.
The TDSZ2 is very simple, doesn't need brake shut offs and stops instantly the second you stop peddling, but it needs you to get sweaty and put in some effort. On the off road trails its actually very good and an equal to the Bosch I have ridden with the plus of being able to remove the speed limit. Downside is the reliability is similar to the early Bafungs, improving as they get used more and if you ride them sensibly they are a rewarding ride. Forget to change into the gear before stopping that you need for the next start and with the added torque and you giving it a big heave, the blue gear can be an issue but resolvable by fitting the widely available brass gear, ride them as you would a mtb bike and you won't have any problems.