It's just my personal preferance but I would never use an expandable for a bear or anything larger than a deer. I just got some 125 gr Montechs made by G5. I am extremely impressed. I did have to touch them up coming out of the box but they are scary sharp and they are exreamly well made. I can't wait to see how they perfom in the field.

Alaskahunter nailed it so I have nothing to add to that.
100 gr is too small for bears You might get the job done but there is some risk involved when shooting a bear with 100 gr,, I have used Montec G5, 125 gr Thunderhead, RM Titanium 125 and also 140 gr failasfe.. all are great, it just come down to personal preference, my choice is Titanium

IMO, after having guided many bear hunters I would say that expandible BH's are a distant second to fixed blade.

A high % of bears we have lost have been with exp. B/H's.

However, if you you not wish to change than only take a perfectly broadside animal and forget any quartering shots. They perform sub-standard on quartering shots.