It's been said many times before, but I'll go ahead and beat the dead horse, the boots need to fit well, that's more important than anything else. As boots get stiffer and stiffer I'd say fit just keeps getting more critical.
You really need to know what you are doing to decide what sort of boots will work best. The lighter, mostly fabric boots such as the La Sportiva Trangos, the Scarpa Charmoz,the Kayland MXT, etc. all hike pretty well, climb rock quite well, and are very light for all there ability. You can climb snow with them fine, they'll kick steps better than a hiking boot and with stiffer crampons a little front pointing is possible although it sucks. They will never really be waterproof or all that warm. They aren't really all that durable either, that's the primary sacrifice for the light weight.
Going all leather will buy you much more durability and water-resistance, along with a little warmth. They will be quite a bit heavier. There are some all-leather boots available that still flex enough to hike alright.
In the realm of insulated, rigid boots there are sort of three categories. Heavy leather boots, insulated synthetic boots, and double boots. The heavy leather boots are warm, can be kept dry for a full day in the mountains (longer with great care) and provide lots of support for front-pointing on moderate to steep ice. The insulated synthetic boots have more ankle flex with a rigid sole, which is not as nice on moderate ice but is great on steep mixed. The double boots are mostly about being warm, and are easier to preserve your toes in difficult conditions for days on end.
It seems like most climbers in the pacific NW have a pair of light synthetic boots and a pair of heavy leather boots. They usually use the heavy leather for trips involving more snow and ice and the light synthetic boots for trips involving more rock, as it seems like the temperature and moisture level follow the climbing medium.
Double boots are rarely called for in the Cascades outside of Mt. Ranier IMHO. The insulated synthetic boots seem to be quite popular with serious ice and mixed climbers but the lack of water-resistance is a problem in the alpine. The light boots get pushed into a lot of snow-and-ice use where they are not so ideal because they are light and nicer to hike in, if you only have one pair of mountaineering boots they are probably what you'll end up with. Remember that fit is critical.
There are some sort of in-betweens. Stiffer boots without insulation. I have used a pair of Scarpa Triolet's to do just about everything. They are just stiff enough that front pointing doesn't hurt to much, but low-profile enough to climb rock well and they flex a bit for hiking. A bit sketchy in the cold though and not what you want to hike a ton in. Not as light as some either. I used a supergaiter to make them warmer and more water-resistant in the winter, which more-or-less worked. This past year I picked up a pair of Nepal's and I've been very happy. On a lot of trips they will be worth the weight.
I hope this helps.