Hi Mike,  [Imagine that] I am considering buying a car.  Should I buy
a Cadillac or Mercedes?  Is $1500 reasonable?  All things equal,
my preference leans strongly towards the Mercedes, but this is never
a case of all things begin equal, is it?!

You mention several "tines" being broken on the Mira.  Not knowing
what that means I'm guessing that a few teeth on the comb are broken or
missing (same thing!).  Those are notes that would be missing from the
music -- or, if it's a dual comb, would be unbalanced as you have only
one note here and two there.  Consider why they are missing and how they
became broken; now what does that tell us about the rest of the comb --
is it brittle or stable?

Your next statement kind of scares me -- "the motor slips".  Mira
motors don't slip.  Maybe the spring slips (this is a known mechanical
fault with the Mira design) but the rest is so over-engineered that
even after 110 years they don't need an overhaul.

In my silly example above I chose to buy the Mercedes.  (Actually, I
decided to buy the Mercedes twice, a 2010 Convertible and a 1958 Ponton
sedan, both in like new condition.)  In music boxes, I have one of each
and I definitely favor the Mira.

Here are a few things you didn't mention:

1.  What diameter of discs?  Regina discs are fairly common in the
15.5" and 11" sizes, other sizes are harder to come across.  Mira
discs are harder to find, but the 18" size is the most common.

2. How many discs come with the machines?

3. Which one sounds better?  Personal taste is all important.

4. Are the tunes good on the discs that come with it?  (I bought a
musical box with discs that I didn't like so I sold those on eBay
and got more.  Fortunately it was only two discs out of 60.)

Good luck -- there are a few good boxes out there to be had!

Eli Shahar