As discussed on the phone, I strongly suggest you go for MBB anyway, and this for 3 reasons:
1. All else being equal, MBB will give you greater opportunities in the future. You will be an alumnus all your life. Right or wrong, people will assume you are a little better, a little smarter just because you have MBB on your resume
2. Going into a boutique or very narrow field is fine as long as you like it - but you are also a little stuck. Going into MBB (particularly BCG) will give you a chance to see other industries and types of projects early on, so you have a broader set of skills and a chance to see what's happening in other areas before deciding Life Sciences is really where you want to spend the next few years of your career
3. Shoot for the stars. Apply to the best companies you can, get all the offers. Once you have these offers,we can look at this again. For now, you should really just focus on getting better and acing these cases - nothing else matters
PS: Now, if you are not sure consulting is for you... completely different question. But if you want to do consulting, why aim for the 2nd tier when you have the capabilties and profile that top tier companies look for?