The first thing to consider is your budget. A analog controller will generally be about $20 cheaper than a digital one. The digital controllers are more versatile as you they have both heating and cooling modes. You can do either with the analog units, but you must remove the cover and switch a lead to a different terminal inside. No big deal, but not as convenient as the digital models. Northern Brewer has them both shown on this link:
NORTHERN BREWER: Fermentation Temperature Control
I have three of the analog and one A419 digital unit. No problems with any of them and the oldest analog model is approaching ten years of use. Go digital if you can spare the cash. Otherwise, or if you need a bunch of them, the analogs might be the better choice.