There's a difference between "pleasing to the ear" and "technical", in some cases. For me, music like Death, or Atheist or Cynic or whatever are very very technical, but for me they're also pleasing to the ear. For others, they might not be (for example, most 13 and 14 year olds will not like death metal at all, much less tech/prog death)
Opeth fall into that "pleasing to the ear prog" catagory, at least for me. They might not be overly technical like some other prog bands (Dream Theater, for example) but they are technical, to a degree.
Both Mike's solos and Peter's solos are pleasing to my ears. At certain times I'll like Mike's leads/solos, and at other times I'll like Peter's leads/solos. For example, I love both parts of the A Fair Judgement solo, but I like Peter's part more because it's the cresendo of it. Mike's buildup is amazing, but Peter putting the exclamation point on it, for me, is what makes that solo great.
On the other hand, I like Mike's leads in Deliverance more than Peter's. I don't really like Peter's solo, but I love Mike's clean leads before the clean vocals come in at the 1:10 mark or so, and I love Mike's solo at halfway or more (I can't remember specifcally where it is)
I don't know why I decided to ramble since it probably has nothing to do with the discussion, but getting back to my point earlier:
They're both technical. You can't deny that. A Britney Spears fan, if he/she had heard Opeth, can't deny that Opeth are more technical than Spears. Whether they think Spears is a better singer/band, that's up to personal opinion, but you can't change facts about technicality, something that both Mike and Peter possess.