[AnssiH]

Generally, no, it feels pretty random to me.

For small purchases I don't care that much (and .de has cheaper shipping to me), but for larger purchases I usually price-compare between .de, .co.uk, .fr, .it, .es, .com as the price difference may be significant (i.e. save me hundreds of euros), and all of those sites have had the cheapest price on occasion.