LNAV preferable over LNAV/VNAV

Take a look at the Mobile Alabama KMOB rnav Rwy 14, should be
available here

http://www.myairplane.com/databases/...s/00267R14.PDF

I notice that lnav/vnav minimums are 660 feet while lnav minimums are
620 feet. My question is, if someone has lnav/vnav authorization, why
wouldn't they prefer to do the lnav, using the glideslope as advisory,
and descend to an mda which is 40 feet below the decision altitude? I
understand the da allows a slight descent below it while initiating a
missed approach, but it still seems the lnav only approach would be
preferable.

Any gurus out there that can provide some input?

Any approaches around with an even greater disparity between lnav and
lnav/vnav minimums?

Stan