Is there any difference between Stocks and Shares ISAs offered by different companies?

my current and savings are with Barclays, would there be any reason to not open a S&S ISA with them also?

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EDIT: thanks everyone for the replies, im going to read up some more about it and buy one of the book suggested on the wiki so i can fully understand what im doing. I'm starting on with a measly £50 deposit whilst i track the (hopeful) growth of it and learn what im doing.