I believe trust is relational. I trust sha-256 more than I trust md5, I trust my grandma more than the NSA, but I also trust the NSA more than I trust ISIS.
So in that context, I trust TOR more than tribler(although they really dont do the same things obviously). As far as torrenting concerns, It may or may not be an unpopular opinion but I think people worry too much. The feds simply aren't going after downloaders. They go after the seeders originally distributing the content or they go after the places distributing the torrents i.e piratebay. While I know some ISP will give cease and desist stuff if they notice you use torrents, I've personally yet to be in that situation. Prominent seeders have long by now figured they need to seed using some anonymity elements and I feel that at least in its current state Tribler would only introduce uncertain amount of risk. If I was in the seeders shoes Id rather stick to whatever setup I have going on that I know works rather than worrying about the plethora of potential 0days that tend to show up in new projects.
Also I looked at their anonymity design and while I cant comment on any of the technical details they very clearly are at risk for bad entry/exit nodes, maybe even more so than with TOR. If im sitting on an entry node, and I see you uploading some new movie before release date, you betcha Im not gunna care what happens with the rest of the torrent or who knows, I've got your address and Agent Mcgee is on his phone with your ISP. I don't even need to be targeting you, cause lets face it: even though TOR gets a lot of bad rep for being for illegal usages, torrents have a much higher ration of 'illegal' content to legit content than even TOR and is more ubiquitous. I can just sit on an entry node and just go fishing for seeders. No more need to identify the original seeder,they come to you first, no more need to hop on some torrent to target a specific individual or content, I can just prosecute whoever comes my way. My intuition is also betting that its easier to become an entry node than it is to be an evil tracker server for the purposes of identifying prolific seeders.
TL:DR: if I was some fed tasked with shutting down torrents, Id be more happy about the prospects of abusing Tribler than the people using tribler are about its capabilities to protect them.