I have the Little Loco also and have the same question. I have tried an Ortofon Rondo Red and an Audiotechnica ART-9. Both sound very good, the AT better but it's probably just a better cartridge. From what I've read the cartridge's internal impedance is probably the most significant spec (the lower the better), so the AT's 12 ohms is pretty low but how does the AT compare with other cartridges with the LL? Don't know.
I plan to try a My Sonic Labs cartridge with impedance of 1 ohm shortly after the new year. Unless people chime in with other recommendations.