Which arduino will be suitable with bill acceptor I want to connect a bill acceptor (protocol ID003) and 3 switches and an Ethernet shield to Arduino. I am building a system that accepts bill and pass on the information to our software. Which Arduino will be the best choice, we need something which will have lot of code and also communication should be fast. 


ARDUINO MEGA 2560 REV3
ARDUINO DUE 
Arduino Uno REV3


--Edit--

This is I want to create:

A bill acceptor connected with arduino. Arduino has 3 buttons. (1. Play button, 2. redeem cash button. 3rd is not necessary).

When user login on machine, I get the details of user account through an API.

When user inserts money in bill acceptor, it enables the play button and add money in users account (If user already has money in account, button will be enabled). User can play until his account is not empty (i.e. if user has 200 in account, he can play 10 times). User can earn or lose money.

I have to send this transaction detail through an API.
If user press redeem button, it will print a slip of account details (Total money in account)

I am using Python.

I need to know which arduino is suitable for this, Ethernet shield compatible with that arduino (I think I am going to use ARDUINO MEGA 2560 REV3, but I don’t know Ethernet shield compatible with this model). 

Also I need some Idea how can I make this. This is first time I am using arduino and bill acceptor.
Define 'lot of code', the Arduino Uno has 32 KB Flash, the Mega 256 KB.
Define 'fast', the Uno/Mega are 16 MHz, the Due 48 MHz
Three switches use 3 GPIO's, shouldn't be a problem on neither of them; the Mega has more GPIOs than the Uno, but both have plenty for your needs.
The Ethernet shield are available for all three
I don't know the 'bill acceptor', add a datasheet.


Conclusion: it depends on what is lot of code, and what is fast.