If a browser is using meta
tags to determine the character encoding, then the first one of such tags takes effect. This has not been specified in current HTML specifications, but it is the common practice and being standardized in HTML5, see HTML5 CR, clause 8.2.2.2 Determining the character encoding.
There is no difference between the two types of meta
tags mentioned in the question. They are just syntactic variants. It is the order of appearance that matters: the first one is used. (It is relatively simple to test this, but you need to use a page that does not have HTTP header specifying the encoding and does not contain Byte Order Mark, since such information would override any meta
tags.)