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First of all, as you're mentioned the reason to change that are cookies - there's no need - see "sub-domain cookies, sent in a parent domain request" on Stackoverflow:

The leading dot in the domain value .example.com means example.com and its sub-domains. Without the leading dot, the cookie is only valid for this specific domain.

 

Note that when setting a cookie, domain values without a leading dot will be prepended with a dot. Only when the domain parameter is not set the user agent assumes the current domain for that cookie.

SEO-wise: If you go with "www." or without is not important, as long as you 301-redirect from the one to the intended one and all webmaster tools know what your intended domain is. BUT: If you would change this in an existing project, keep in mind the already existing backlinks and if it's worth to redirect them and possibly lose some link juice.

First of all, as you're mentioned the reason to change that are cookies - there's no need - see "sub-domain cookies, sent in a parent domain request" on Stackoverflow:

The leading dot in the domain value .example.com means example.com and its sub-domains. Without the leading dot, the cookie is only valid for this specific domain.

Note that when setting a cookie, domain values without a leading dot will be prepended with a dot. Only when the domain parameter is not set the user agent assumes the current domain for that cookie.

SEO-wise: If you go with "www." or without is not important, as long as you 301-redirect from the one to the intended one and all webmaster tools know what your intended domain is. BUT: If you would change this in an existing project, keep in mind the already existing backlinks and if it's worth to redirect them and possibly lose some link juice.

First of all, as you're mentioned the reason to change that are cookies - there's no need - see "sub-domain cookies, sent in a parent domain request" on Stackoverflow:

The leading dot in the domain value .example.com means example.com and its sub-domains. Without the leading dot, the cookie is only valid for this specific domain.

Note that when setting a cookie, domain values without a leading dot will be prepended with a dot. Only when the domain parameter is not set the user agent assumes the current domain for that cookie.

SEO-wise: If you go with "www." or without is not important, as long as you 301-redirect from the one to the intended one and all webmaster tools know what your intended domain is. BUT: If you would change this in an existing project, keep in mind the already existing backlinks and if it's worth to redirect them and possibly lose some link juice.

First of all, as you're mentioned the reason to change that are cookies - there's no need - see "sub-domain cookies, sent in a parent domain request" on Stackoverflow:

The leading dot in the domain value .example.com means example.com and its sub-domains. Without the leading dot, the cookie is only valid for this specific domain.

Note that when setting a cookie, domain values without a leading dot will be prepended with a dot. Only when the domain parameter is not set the user agent assumes the current domain for that cookie.

SEO-wise: If you go with "www." or without is not important, as long as you 301-redirect from the one to the intended one and all webmaster tools know what your intended domain is. BUT: If you would change this in an existing project, keep in mind the already existing backlinks and if it's worth to redirect them and possibly lose some link juice.

First of all, as you're mentioned the reason to change that are cookies - there's no need - see this answered question on Stackoverflow:

The leading dot in the domain value .example.com means example.com and its subdomains. Without the leading dot, the cookie is only valid for this specific domain.

Note that when setting a cookie, domain values without a leading dot will be prepended with a dot. Only when the domain parameter is not set the user agent assumes the current domain for that cookie.

SEO-wise: If you go with "www." or without is not important, as long as you 301-redirect from the one to the intended one and all webmastertools know what your intended domain is. BUT: If you would change this in an existing project, keep in mind the already existing backlinks and if it's worth to redirect them and possibly loose some link juice.

First of all, as you're mentioned the reason to change that are cookies - there's no need - see "sub-domain cookies, sent in a parent domain request" on Stackoverflow:

The leading dot in the domain value .example.com means example.com and its sub-domains. Without the leading dot, the cookie is only valid for this specific domain.

Note that when setting a cookie, domain values without a leading dot will be prepended with a dot. Only when the domain parameter is not set the user agent assumes the current domain for that cookie.

SEO-wise: If you go with "www." or without is not important, as long as you 301-redirect from the one to the intended one and all webmaster tools know what your intended domain is. BUT: If you would change this in an existing project, keep in mind the already existing backlinks and if it's worth to redirect them and possibly lose some link juice.