Okay, since you asked, here's what I've learned over the years, in no particular order:

Aluminum:
- aluminum is the most efficient at heat transfer; it will boil water a bit faster, and make best use of a modest heat source (alcohol/Sterno)
- aluminum pots will "hiss" rather loudly as they boil water
- plain aluminum pots noticeably change the flavour of food and drink, though you do get used to it
- aluminum is very good regarding weight and durability for a given volume
- do not try to drink from a hot aluminum pot/cup; you will give yourself a nasty burn/scald
- if I was using aluminum a lot, I would pay the extra money for the new anodized versions

Stainless Steel:
- stainless steel has rather poor heat conductivity compared to aluminum
- it's easier to clean
- poor heat conductivity has a bright side: you can drink directly from a hot pot that's 3/4 full without burning your lips; and it's slightly more forgiving in terms of scorching your supper
- lightweight stainless steel pots/cups are readily available these days; the weight penalty compared to aluminum is less than it used to be
- stainless steel is available everywhere, including discount stores and secondhand stores, for cheap

Titanium:
- wins on weight, hands down
- very bloody expensive
- might be best choice if you're boiling tea at Everest base camp

Personally, I have pretty much settled on stainless steel for utility, durability and cost. But I'm open to beguiling suggestions from catalogues. :-)