Ok on another note I do like W8JX idea of not using the booster junk. Raw battery feed is the best thing.
I also agree with not using a battery booster.
If you're not careful with one of those, it's too easy to over discharge a battery using one of those.
That will get expensive very quickly.
The MFJ-4416B has a selectable cutoff of 9, 10 or 11V (default 10V). The intent being to avoid battery over-discharge damage. The other boosters I've seen have similar protection.
If you run the rig straight off the battery, are you careful to have a voltmeter attached, and never accidentally over-discharge your battery? There's risk that way too.
To me it boils down to this: I would try running directly off a battery first. But if a particular radio misbehaves even above 11V, I would consider a booster. But maybe a different radio is more practical.