I would not use Avianca for my primary program. Whereas they have some gems in their award chart, they allow you to buy miles cheaper than flying, so if you want to take advantage of their flights then you might as well buy them. The biggest problem with them though is that they are an unknown. Their redemption chart has changed a few times without notice, their availability has disappeared at times, customer service is rough for some, and lots of speculation on how long their rates can remain low. The general rule with them is buy miles, and only then when you have some trips in mind or will use them fairly quickly.

I don't know about KF much, but they actually have a discount when booking online which I have used, so keep that in mind. Also, I did have some issues about certain fares on them not crediting to UA in the past.

It's tough when you're varied, but maybe look at who you fly the longhaul business flights on, and base the decision around that. Given that business often earns more miles for status, like 150%, you might be able to earn more in a particular program as well as attaining status.

All that being said, I keep one account for each alliance, so three programs isn't the end of the world. But two would be better.