Q: What are the differences between the Bina 23b Reg. and the Bina 23b Dlx.?

A: First we should note that all Bina harmoniums say "Deluxe" on them. 

Regarding the ever popular 23bs, our description is a way to differentiate two slightly different instruments. These harmoniums are equal in quality, sound and about $50 different in price. Basically, the Deluxe is slightly larger. It is 2 inches longer, with 3 extra notes (it goes to high F, whereas the Regular goes to high D) It is slightly heavier, and has a 6 fold side bellows. The Regular has a 3 fold bellows that attaches on the bottom. The Deluxe has 4 drone notes (usually C#, D#, G#, A#). The Regular has 2 drone notes (usually C# and G#).

The advantage of the Regular is that it is smaller and lighter and thus more portable. It easily fits in the overhead of an airplane (by some standards the Deluxe is too big). This is the instrument that Jai Uttal plays.

Most people don't use the drones, but if you do, and the extra choice appeals to you, then the Deluxe might be your preference. Likewise, if you are used to, or prefer, the side pump bellows, then this would be your choice.

The Regular model complies with all the airplane carry on size restrictions. The Deluxe model will not fit in all the flights since it is a couple of inches bigger. 
P.S. Please confirm the size allowed by your flight too, since their sizes could change without us being aware.

If you did a "blindfold test" on these two instruments, you would not be able to tell the difference by sound.