Hi
Scotch and Soda has almost become a classic of magic. To start off with there are many threads already on this subject, which could be found using the "Search" option at the top of the screen, or the review Index in the reviews room.
I have pasted some of the more obvious links below, but it is always worth checking first and adding a query like this to an existing link.
There is also an excellent resource for buying magic on the internet call
www.bargainmagic.co.uk This website will allow you to compare prices with many of the UK based magic selling websites.
As well as the classic scotch and Soda there is also Eddie Gibson's "Coin Uniques", which are pretty much the same effect, although imo slightly easier to use. These come in a variety of coins, such as £1 and 1p, 2p and 10p and I believe a 2 Euro and something - although reviews here would suggest that that one isn't as well made.
The versions of the official scotch and soda would seem to be.
Half Dollar and Mexican Centavo
Half Dollar and old English Penny
As for the Scotch and Soda Euro version, I know nothing about it.
There is also an effect called dime and penny which I am sure is the same principle.
As for what is the best. It is really up to you. I would say that the same effects can be done with one and all, so it is all down to how you wish to present it. For ideas. look through some of the old threads.
There are also various booklets called such things as "25 ideas for..." that are wort looking at for ideas.
Talk Magic Links
http://www.talkmagic.co.uk/ftopic1838.p ... ght=scotch
http://www.talkmagic.co.uk/ftopic1298.p ... ght=scotch
http://www.talkmagic.co.uk/ftopic898.ph ... ght=scotch
http://www.talkmagic.co.uk/ftopic515.ph ... ght=scotch
http://www.talkmagic.co.uk/ftopic331.ph ... ght=scotch