Mountaineering boots

Looking at options for B3 single boots, will be using these mostly for Springtime in the Cascades (Mt. Hood, Adams, Shasta, Three Sisters, etc.) I have tried on several and have narrowed it down to LaSportiva Nepal Cube, or Scarpa Mont Blanc Pro.  Various forums call these "equivalent boots" but after trying both on there seems to be a pretty significant difference in stiffness around the ankles.  LaSportiva seems more supportive/stiffer around the cuff, Scarpa seems to offer more ankle articulation. I'd make the choice purely on which ones fit best, but in this case both brands fit my feet pretty well, and I've gone back & forth with Scarpa or La Sportiva for climbing shoes and approach shoes. Will be used mostly for long snow hikes with crampons, will get into some steeper terrain but not planning on doing much vertical ice climbing. Any advice on which boot might be the better choice?  

Since none of those objectives require any steep ice or mixed climbing, the level of support in that type of climbing is not critical, and you can just get whichever boot you prefer for other reasons such as fit and cost.

Note that for many of those climbs, a more typical boot choice might be a 3/4 shank “3 season” mountaineering boot, as opposed to the full shank winter boots you mention.  This is definitely the case on Adams and Sisters.  Hood can be a bit steeper and a bit colder (as it is generally climbed earlier in the season), so the warmer boot can be justified, especially if you have cold feet.

Thanks for the advice, yeah I have the 3/4 shank  3 season boot already covered (Scarpa Ribelle HD) Seems like it would be good to have something a bit warmer / stiffer available also for colder temperature, early season and steeper terrain

The Ribelle tech 3 hd/ Phantom 6000 combo covers almost every base for me