Props on the poll! I think more of these polls covering a variety of treatments would be a good way to summarize this forums user's experiences. Got to break through the voter apathy; however....
Liquid all the way!!! I lost ground when I switched to the foam. I had been on liquid for four years with great results prior to that. In my opinion the foam is too strong (meaning the amount absorbed).
Logically, liquid should be the superior. At least, if you're talking about Rogaine, which does not have the propylene glycol (agent that penetrates the skin) Minoxidil has. Granted, for application purposes Rogaine is easier to apply, obviously. You can diffuse it easier than you can with concentrated liquid. The other downside to the liquid is that it's easier to run down your head. Liquid minoxidil can also accidentally spill if you knock it over (sh1t happened to me once and I went ballistic). All you need however is to be careful with the thing. This reminds me of yet another con. Since it doesn't come out via pressure nozzle like Rogaine, it gets exposed to the air/moisture in air which can slightly weaken it as it gets used over the month. Chemically, liquid minoxidil is better.
When you still have a lot of hair, the foam is very crappy to apply, especially when your diffusing all over (in the genetically affected area) like me. So, its just so much better with the liquid (now using kirkland) for me.
What does suck however, is that my hair gets greasier and thus optically thinner with each day, until I wash it and then the whole process starts over again.
...I was JUST in another topic someone made who was using the kirkland version, saying it's very greasy etc., so it could just be that, that version of min is made of ***.