Never having dived with a computer before I was faced by the same choice a
few months ago.  I went for the Quantum and have been very pleased with it,
even though I do not at the moment intend to use the second gas setting or
even enter the realms of deco diving.  Nice easy to read screens and even a
dimwit like me managed to get the hang of the settings and modes within
about half an hour.  Very easy to set up before diving.

I didn't like the strap either so I drilled holes in both pieces of the
strap as close to the computer as I could get.  I then threaded a length of
thin bungee through this, which is tied to give a snug loop around my
drysuit wrist.  If the strap should come undone or one side of it fail I
should still be left with the computer attached to my wrist.  It also makes
the thing easier to put on if you are bobbing about in a boat.

Cheers,

M