I am not an expert with either LILO or GRUB, but am more familiar with GRUB. I was only starting to learn the basics of LILO (since I switched to Slackware) and now I see 14.1 includes GRUB.

I think I will be better off knowing one really well and just avoiding the other than trying to learn both. Which do you think I should learn?

I don't want to invest in LILO if it is going be increasingly less popular and eventually go away, even if it is around for some time.

So far, I like Slackware better than other distro's I've used. If most Slackware systems continue to use LILO and GRUB is just a small concession to make things easier with those who want to use it, I'd rather learn LILO.

GRUB seems a little easier to work with if it is misconfigured, and that could just be my familiarity with it. otherwise both do their job well.

Grub is added to the Slackware repositoriy for mainly one reason: It has better support for UEFI than Lilo. Lilo is still the default option and will not go away soon.