Its a hard choice as they are both really good in terms of bass, vocal, sound stage and clarity. The TG334 is a very warm IEM but the despite that, it has a unique ability to pump out a lot of details with great clarity without needing much treble, in other words, it does not require much treble to trick the ears to be "clear" and that is really something for an IEM.
The set back is, TG334 hiss quite a lot, it hiss on most phones and many amps out there. I finally get the hiss under control with dacport 1 ohm mode so If you can get pass that hiss, it’s a wonderful IEM. SE 846 too has its unique ability ... first the bass.. , the sub bass just rumble softly when call upon and disappear completely when not needed. It’s like adding a very fine tune sub-woofer to a floor standing speaker. The TG334 too has that level of sub bass, but I find it to be too thick to disappear completely when not needed. Don’t get me wrong, I am not saying that it leaked badly to the mid, it does not, but when compared directly to Se846, the sub bass level is not as refine. Think of a TH900 sub bass and LCD-3 sub bass, these 2 headphone has been rated as having the very best bass out there in quality and quantity but yet, they are completely different kind of bass. The TG334 would be LCD-3 type of bass, while the Se846 lean more towards TH900 refine bass level.
Both have very good soundstage, but I prefer TG334 type of soundstage, very 3D and tall. They are both very good, but both pales in comparison to say EX1000 or K3003. These 2 IEM is about the widest I have heard but then they are not as 3D. Both TG334 and SE846 has pin point accuracy positioning... not sure which one is better, they are both similar.
The good thing is SE846 comes in different flavors with 3 filters. You can pick your flavor and if you want to resemble more of TG334 tonality, get the custom sleeves. The bass and vocal becomes thicker and treble reduce quite abit. So 4 flavors to choose from.