All reviews should be subjective with an opinion ! That is the point of it. Otherwise they are not reviews, and become pathetic information brochures that people translate or regurgitate and place on websites purporting to be news.
A review should be subjective but unbiased.. , with reasoning and transparency in explaining how and why the opinion was formed. When explaining, evidence backing their viewpoint will also help to solidify their argument.
An in depth test is obviously extremely helpful. Numbers will help so long as they are used to solidify or prove a stance. If it is too close to call then people can use those figures to make their decision but will also be swayed by the reviewer's opinion based on trust of their expertise, demostrated knowledge, or history.
The information will then be weighted against other reviewers to determine if there is a trend or concensus. Subjectivity is fine so long as it is listed or shown in detail what settings were used for replication.
If a reviewer cannot give their own unbiased preference , then I would think they were either uninformed or a salesman for the company.