Maybe, maybe not.  For example, a rate of 2-3 dives per day means that
you're going to be spending around 21 hours/day out of the water.  

Even if you budget 12 hours for sleep, that still leaves roughly three
times (3x) as many waking hours doing stuff topside that's not diving.

As such, perhaps the two island's topside elements are important to the
visitor:  do they prefer hiking and caving, or birdwatching?  

Because like everything else, what constitutes "Best" is subjective.

For a diving example, in the Northern Hemisphere, walls that are on the
north side of an island are in shadow.  If you're into UW photography,
it may or may not be important to you.   So if you want dive on a sunlit
wall face, you'll need to find walls on the south side, not the north.  

On the Brac, there's Rock Monster Canyon, Son of Rock Monster, Crab
Alley, Wilderness Wall, Inside Out, Manta Canyon, Sea Feather Wall,
Tiara Tunnels, and Anchor Wall ... just that I can recall of offhand.

Now try to name four southside wall dive sites on Little Cayman.

Hmm.  

FWIW, I stumped myself on this one.  I did find that there's actually a
total of five (5) identified southside wall sites.

Granted, some don't like these Southside walls (on LC or the Brac)
because they're 'deeper', but we also have the trade-off that some stuff
is generally only seen at certain depths, too.

Also, it does tend to seem to me that there are a significant group of
divers who seem to measure a dive's goodness not by the quality of what
they've seen, but by its duration.  

Yes, its great that *some* of Little Cayman's sites has shallow 15-20fsw
gardens to have an enjoyable and extended safety stop.  This does
assume, however, that the shallow flora present appeals to you.  Do note
that in some areas, its a transition-to-hardpan, which isn't necessarily
a type of reef structure that appeals to everyone.  

Moving on to other factors, since all but one of the Little Cayman
resorts are on the Southside of the island ... and the famous Marine
Park is on the opposite side ... for those divers who might be a bit
susceptible to sea sickness might not appreciate having to *always*
spend at least 15 minutes on "the rough side" of the island (each way)
as well as a typical 30+ minute ride each way.  Sure, the crossings from
the Brac to LC are 45 minutes, but the operations wait until a calm day
to visit.

All in all, its a trade-off...and don't get me wrong, for I enjoy Little
Cayman just like I enjoy Cayman Brac:  over just the past 12 months,
I've spent 4 weeks there, between the two islands.

Our timeshare's at the Divi Tiara.  The hotel seems to be in good shape,
but the company's been jerking the TS owners around...we're in Year 4 of
a "quick" renovation and I recently heard that the Government may have
shut down the TS work because they weren't meeting building codes??  We
like the people on the island, the resort, food and diving op, but we
would not recommend that anyone buy a timeshare from them like we did.

We've recently given some of our business to Brac Reef Beach Resort down
the street.  They did quite well.  We expect to do so again in the
future.

On Little Cayman, we've stayed at Pirate's Point, Paradise Villas and
the LCBR.  

LCBR:  didn't care for the noise from the bar, and noticed that with it
sitting in the middle of their complex, wasn't necessarily easy to
escape.  3 short dives/day.

Paradise:  didn't care for having to fend for ourselves for meals.  
Nice, generally quiet location.

Pirates Point:  Gladys Howard is a hoot.  Great food, quiet setting.  
Only 2 dives/day, but they're unlimited in length...only real problem is
that this results in lunch being at around 2pm.  You also get in a van
to go to the boat dock, which some people don't care for.   Ready to go
back.

Southern Cross:  look up HW Skip Weldon's trip report.

Sam McCoy's:  the only place on the north side.  A friend goes here
2x/year and enjoys it.  He's found a way to get in 4-5 dives/day here by
doing shore dives on his own in the late afternoon...reports that the
reef sharks get more active at this time of day.  Might have to go down
sometime with him to check it out.

I'd be a bit concerned about the weather in March  - it will probably
still be in the "winter" mode where it tends to blow more out of the
N/NE.  This makes the North side of Little Cayman a bit of a rough ride
and can kick up the sand inside of Jackson's to make viz a bit green.

-hh

Why bother ... Dove both though it has been a while. Both have pros and
cons. The OP did not say whether they were just interested in diving or
other activities apres.  I happen to like to climb so I go to Brac so I
can climb and dive. Climbing may not be your tea but some people
sometimes like to balance their underwater fun with topside fun.

Now I rarely use a hotel and not big on all inclusive places. I prefer
to find a cottage to rent and do my own cooking going out a couple
times during a week. Hard to find that on LC.  Easier on CB. If you do
this on CB you will need to rent a car. Ah another factor on deciding
which island.

Want to fly directly into CB from the states? Completely, possible for
CB but can not do that on LC. Gotta take a puddle jumper. Add another
$400 or so to the trip cost.

So I would bother with CB depending on the type of trip desired just as
I would for LC.

Your milage may vary

Allen