I would start with whatever you find most appealing. I'll preface my following comments with the fact that even referring to myself as a hobby knifemaker would be a stretch as I still haven't completely finished my first slip joint (though I'm getting close). I kept reading about the difficulty in getting the "walk and talk" characteristic of a good slip joint. Although it is challenging and takes patience, which is something I usually lack, it is certainly doable, especially if you take advantage of the experience, guidance and resources available here in this forum. There are several WIPs, tutorials and knowledgeable makers here who are eager to guide us newbies. All the fancy tools help, but they aren't required. Patience and attention to detail are though.
I've read that the mechanisms of liner/frame locks are easier to get right, but I have no first hand experience with these. They certainly seem to be more popular. I don't care though, slip joints are my thing!
