I like both ways.
Some songs are easy to learn in a linear way. I did this with I Love Rock and Roll. Once you have that first riff with the bend in it, the rest of the song is just variations on it.
On Mississippi Queen, I've broken it down to different riffs, each one repeated in different parts of the song. I had to do it this way because I was learning new techniques at the same time (tremolo's mostly). Once I get all those riffs and phrases down, I'll stitch it together and learn the sequence they go in.
I also work on several songs at the same time. In a typical practice session, I'll do some scales or something to 'loosen up', then shoot through songs I have already learned to keep getting better at them. Then I'll work on one new song till I get frustrated or tired of it, then try the next song, etc.. The songs are usually very different.
Do whatever works and don't forget the 'have fun' part. If it's all work and sweat, then you'll lose your motivation and practice less etc etc.
GG