Full disclosure: I own neither of them.
Having said that, I have researched both of them, extensively, since I was considering buying them both at one time or another. When I had a chance to play the TRBX 304, it just wasn’t for me. Not that there was anything wrong with it but choosing an instrument can be very personal. What stopped me from buying a Sire V3 was that I could never find one to try out.
I’ve never been able to find anything but positive reviews on both.
If it was me, and I had to choose between the two without having a chance to get my hands on either, I would choose the Sire V3 just based on the feature set. They include a lot of stuff that you usually only see in much higher end instruments. Like an active/passive switch, rolled fret board edges, and string through body.
However, if you’re worried about weight, go with the TRBX 304. As @Rob1 said, it definitely wins in this category. Also, quite a few people around here have them and I’ve never heard anything but good stuff from them.