Take the earlier flight. As posted upthread, you have to change terminals landside, re-clear security etc. Every time I'm done a UA-to-TBIT connection at LAX, after waiting 10 minutes for the stupid bus, the stupid bus never came and I ended up walking the 15 minutes or so up to TBIT.

Also keep in mind that at least some UA *A partner international airlines still don't like UA-issued boarding passes and will insist on you getting a new BP from them. Add time for that.

Take the earlier flight. You're 1K, enjoy the new Star Alliance Lounge in TBIT. If you have a real long layover, you can appreciate it even more by spending time in the UA terminal RCC scarfing for crummy crackers before going to TBIT for sushi, sandwiches, noodles, free alcohol, and deserts from around the world.