Scarpa VS La Sportiva Sizing for Mountaineering Boots

So I have an opportunity to obtain some Scarpa Phantom Guides at a deal I can't pass up, but no where around me has Scarpa Mountaineering boots. I figured I'd pole here before bothering a rep.

2 Options in my mind

1)Anyone know how close the lasts in say the Phantom Guide to some of their hiking and backpacking boots? There are REI's around that stock those. Or even how different is the lasting from the Inferno to a Phantom Guide.
2)I know my La Sportiva sizing in the Batura 2.0, Nepal, and the silver Trango. How do they compare to the Phantom Guide?

Thanks

I'll try to answer your question but I am not quite sure as I have never worn Phantom guides.

I'll start out by saying that I wear a 9 (42.5) wide in Asics

I've worn the Nepal at 42.5 and they are super narrow on me.

I switched to Mont Blancs at 42.5 and they are a slightly tight but seem to work really well.

I just bought a pair of Rebel Pro Gtx at 43. The last compared to the Mont Blancs is definitely a bit more narrow but also the shape is a little bit weird compared to the Mont Blancs at least on my feet. I have yet to really go out and test them though.

Length is about the same on both brands, but Scarpa has a wider last.

Depends on the shape of your foot but I wear the same size LS and Scarpa. Phantom Guides run wider than LS Batura and Nepal Evo's.