If you need Lo, or runes up to Jah including Jah, LK is best area in the game. And only p7/8 LK, not p3/4. Don't waste time on p3/4, really.
Here are known LK patterns. As you can see, on players 7/8 you get far more runes than on any other player settings, especially interesting is Sur rune which has 11 known patterns which means you get one Sur rune per 993 runs which is amazing. Nowhere else in the game can you farm Sur/Ber that fast at average. I exclude luck from this, you can be lucky and get Ber + Sur at the same cow run, or same Travincal run. No, I'm talking about average runs needed, and at that LK is far superior to any other area in the game. Only players 7/8 LK, other player settings are considerably worse at dropping runes.
Considering Lo alone, I assume you will cube Ohm runes to Lo unless you have some plan for Ohm runes as well. In that case, including Ohm runes into equation, at p7/8 LK it takes at average 2427 runs to farm/cube 1 Lo at average. Interesting players settings is 5/6 for farming Lo runes since there are 4 known Lo patterns, and only 2 known Ohm patterns. At players 5/6 it takes at average 2184 runs to farm/cube 1 Lo at average, which is better than on p7/8, however difference is so small at farming Lo runes and you have so much better chance to get Sur/Ber as you farm, as well as charms/jewels or whatever you collect. So, players 7/8 LK all the way.
Comparing with Travincal now. If you farm players 3 Travincal with 55% Item Find barbarian, it takes you at average 2540 runs to get Lo, or if we include Ohm runes and possibility of cubing them to Lo, it takes at average 1451 runs to farm/cube Lo in p3 Travincal with 55% Item Find barb. So, we have 2427 runs at LK p7/8 and 1451 runs at Travincal p3 55% hork.
Now it depends on how fast you can run certain area. If your Travincal run is 2427/1451 = 1.673 times slower than LK run, or faster than that, then Travincal will net you better chance to get Lo rune. Assuming it's quite easy to run LK at 30 seconds, which should be doable with a little practice, it means that if you can run Travincal below 50 seconds average, then Travincal will give you better chance at getting Lo rune. But, players tend to run LK in 25 seconds or faster with some practice, which is really not that fast (several players have ~20 seconds or faster average LK run), that means you have to run Travincal faster than 41.8 seconds to be better target at farming Lo rune. Or if you manage to get 20 second runs, then you should run Travi faster than 33.5 seconds.
Perhaps Travi is comparable with LK at farming Lo runes, but Sur/Ber is different story. To get Ber assuming you cube Sur to get it as well, at average it takes 1285 LK p7/8 runs. In Travincal p3 with 55% Item Find barb, it takes at average 1963 runs to get/cube Ber. Considering Travincal is much slower than average LK run, we can easily conclude how much better chance you have at LK to farm Sur/Ber compared to Travincal.
Jah rune. In Travincal, considering you can cube Sur/Ber to Jah as well, it takes at average 1724 runs to farm/cube Jah. In LK, it takes at average 2570 runs to cube Jah. Again, 2570/1724 = 1.49, so if your Travi run is 1.49 times slower than LK, or faster than that, it means you will farm Jah faster there than in LK. If you don't wanna cube Ber to Jah, then obviously you will be better farming at Travincal where Jah can drop directly, every 3075 runs at average.
Then, there is Cham. If you are after Cham, go Travincal. As simple as that. You will get one every 4613 runs at average. Or 5140 LK runs at average to cube Cham, but it probably isn't worth it to cube so many runes for it.
To farm small charms, grand charms, jewels and gems, LK is faster than Travincal. Again depends on how fast your LK and Travi run is, but it's generally like that. Travincal will net you some useful uniques, more rares and facets.
Hopefully now you have enough informations to decide will you go Travincal or LK. Cows are worse than both, I would say don't waste time on them, but do so if you want. My general opinion is this: For anything up to Jah, LK p7/8 is the king. For Cham Travi is the king. For charms/jewels/gems LK is better than Travincal, Travi is better for experience, some uniques, more rare items like rings etc., and most notably rainbow facets which drop quite frequently in Travincal.