Avoiding the US transit immigration hurdles is a reason not to do the third option with UA.
If you like the quick connection take KL: there is a chance of middle seat in C and sleeping in the not so flat seat though.
The LH option: the only negative I can think of is the extra connection (extra travel time) and if you get the non-refurb F on the a346 (more a nag) but F is F and the service will be more personalised than in C. Get your connecting avianca flight in the same PNR and in case of missed connections they can rebook you automatically.
Last edited by HadesNL; Jan 10, 2012 at 3:40 pm