I have read that one reason the equipment reviews are different is because of housing issues. British and European houses tend to be smaller than those in the USA. The smaller rooms will cause a difference in how amplifiers are rated due to fewer watts being needed for a given loudness. This also causes speakers marketed in Europe to be smaller and probably more efficient overall, leading to yet another form of review bias.

Many American audiophiles would consider a 25 watt solid state amplifier as too small , but the European reviewers color their tastes to some extent for their audience. Since we in the US are less likely to consider a 25 watt amp as adequate, our perspective is somewhat different and few amplifiers with those kind of power ratings get US reviews.

I realize that some American audiophiles just love their 5 watt SET, but in spite of that love affair, flea power SET has never become mainstream.

So it would seem that the reviews end up with different conclusions because the listening environment is different.