I think option a is better than b. It would be a better source and it probably means less work for you as well. But if you choose option a, I think the combined Swedish rating should count as more than one source. Here's a suggestion that just popped into my head:
Number of reviews for MCC calculation = floor (ln (#reviews at kritiker.se))
This means that you take the natural logarithm of the number of reviews and remove all decimals
Example: 35 reviews = floor (ln (35)) = floor (3.56) = 3
(3-7 reviews = 1, 8-20 reviews = 2, 21-54 reviews = 3)
(Cutting the decimals will make your presentation look cleaner and it might make the job easier for you, otherwise there's no need for you to do that)
Alternatively - if you don't think that "4 reviews" from Sweden for the First Aid Kit album is too much - you could use
round (ln (#reviews at kritiker.se))
This means that you round the logarithm value to the nearest integer
Example: 35 reviews = floor (ln (35)) = floor (3.56) = 4
(2-4 reviews = 1, 5-12 reviews = 2, 13-33 reviews = 3, 34-90 reviews = 4)
A third and simple alternative could be to just count kritiker.se as two sources.
In any case, you don't have to worry about the bees and horses.
Krikiter.se has done the job for you and translated all ratings into a 1-5 scale.
I was also surprised to see Gaffa listed at kritiker.se. I don't know about the relation to the Danish magazine.