What is the advantages and disadvanges to getting a B-foot when purchasing a new flute, besides the price?

Well, it depends. On the older flutes, a B foot tended to add a bit of darkness, but would add a little resistance making the 3rd octave more difficult. On most modern flutes, there is very little difference sound wise. The main advantage is that if you ever run into a piece with a low B (I believe there are about 70-80 pieces with a low B), you are able to play it. Most of the time, the B key is unused. The B foot will add a bit of weight, so if you have arm problems , a C foot (or even a D) might be better.

A D foot??? I have only seen one of those before and I don't think that they come standard on any intermediate to pro model flute.

She didn't say what kind of flute she was looking for, so I just gave the most complete answer I could. If it's an intermediate flute, then a D foot is almost certainly out of the question.

Not really. The gizmo associated with the B key can be used as a C facilitator, but a C foot flute can play C4 just as easily as a B-foot with a Gizmo. The whole idea behind the gizmo is that it essentially transforms the flute back into a C-foot model (by closing only the B key), which as I said, historically has been the easier one to play the 3rd octave on. On most modern flutes, you don't really need the gizmo (you can play C4 without it), but it can (depending on the individual flute) make the C4 more in tune, or open the tone up a little.

I find C4 easier with a c-foot

I find C-4 easier one someone else is playing it. Lol!

that's always good too Kara, the whole low B thing is interesting as, being in asia again last month, one rarely sees a bfoot flute, same in europe, at least on the student level, real american thing for young people

I dont see how closing the B key on a B foot makes it like a C foot - that isnt the way the physics works. I must admit that the first time I played a B foot flute I was surprized by how much difference the gizzo makes - however, that same flute has an outstanding top octive which I attribute more to the head that the foot!

The notes on a flute are determined by the open holes (especially the first one down the stack, though the others do play a role, as illustrated by the difference in pitch when you fork a high F), not the closed ones, so by closing the B key on the footjoint, you leave open the same number of keys you would should you be playing a C4 on a C foot instrument. It has essentially become a C footjoint, but with a extra bit of tubing at the end. It's all about the venting of the air from the flute.

The notes on a flute are determined by the open holes (especially the first one down the stack, though the others do play a role, as illustrated by the difference in pitch when you fork a high F), not the closed ones, so by closing the B key on the footjoint, you leave open the same number of keys you would should you be playing a C4 on a C foot instrument. It has essentially become a C footjoint, but with a extra bit of tubing at the end. It's all about the venting of the air from the flute.

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Sorry for the double post.

Advantages:1) You can play a low B. If you can play a low B, which will be very difficult if the flute has any leaks at all.
2)Anyone less informed will assume that, since your flute has a low B, that it is a high-quality flute. Mostly because:
3)Most flutes which are an upgrade for any student flute sold in the U.S. have a B-foot, so specifically asking for a C-foot in a new upgrade flute will likely cost more.
Disadvantages:
1)It weighs more, and the case is longer and won't as easily fit into a bag, if it's a french-style case.
2)There is one more key to service
3)You may possibly have trouble getting your fingers in exactly the right place to play a low C, on a B-foot.
4)You are paying more for the current fashion rather than for a feature that you will likely use. One gal told me she really wanted a low B, to play with the piano music she had. But really, it is hard to get a low B out of a flute at any appreciable volume. Just play it up an octave. If you ever get to play in the Symphony, and have a low B to play, you can either buy a B-foot and have it fitted to your flute, or borrow someone else's flute for that piece.

I have a Yamaha 800-series flute that I found on eBay. I bought it for the same price that the Yamaha 581 flutes were going for. My flute has a c-foot, so it went cheap.

I have recorded and recently performed several pieces with a low b and happened to be recording and rehearsing with the composers, both easily provided an optional note to play, they need to do this as low b is not always so common in other countries

There is also one more option, albeit a bit more expensive than Micron's. Eldred Spell (and probably others) sell silver extensions that do the same as Micron's plastic tube. For $75, it'll let you get the B without having to pay the hundreds (or possibly thousands depending on material and maker) of dollars to buy an entire footjoint, and as it just pops into the end of the flute, there is no need to trim tubing or fit plastic tube over the foot of the flute. Maybe not the most economical option, but a good one nonetheless.

good suggestion, I didn't know about that, good thing to have in ones gig bag