I was on animal insulin (pretty sure I had beef as well as pork) for the first 12-14 years. When 'human' came in I was pressured to switch, which was a total nightmare both in terms of diabetes control and quality of life. Not simply change/loss of hypo symptoms or feeling off-colour, but big personality changes including a violent temper. DSNs very dismissive of problems. After a battle got switched back to pork (apparently fewer people had problems with pork compared to beef) and the side-effects of 'human' all settled. Still not good control but at least I got back some quality of life, hypo awareness etc.
When Lantus and Humalog came along, I was doubtful after previous experience. Agreed to try them on strict understanding I could return to pork at the first sign of trouble. Happily though, with analogs no hint of the side-effects I had with 'human', control improved somewhat but for me Lantus didn't do what I was promised (elimination of night hypos). Two years ago I switched to Levemir, and best control so far. Levemir certainly keeps my bs more stable than other basals and no nasty side-effects.
So I'd come down in favour of analog, but if I any doubts I'd want to revert to pork, but that's just my personal experience and my body. If Lantus was the only analog basal I might think differently though. I was surprised to get on well with Levemir, just shows even if you've had bad experience with human or analog, keep an open mind. If what you're on doesn't suit, try something else but on the basis you can switch back if it doesn't help.