What's new on IELTS with Fiona

I saw both options being used in the SAME text today, so I googled it and found differences of opinion.

At the top of Google search was this theory:

The phrase "compared with" is used to compare similar things, while the phrase "compared to" is used to compare dissimilar things. [Expertsglobal.com]

I tested this theory using this BBC article about health trends.

• Only 16.4% of adults currently smoke, compared with 19.9% five years ago.
• The UK has the eighth highest proportion of the population eating at least one portion of fruit per day (63%) - compared to the OECD average of 57%.

Preply.com says the opposite (I've corrected their grammar so that it makes more sense but I still don't understand it):

"Compare to" expresses similarity between two things. e.g. I compare my work to that of  Dickens. "Compare with" suggests that the differences between two things are at least as important as the similarities. (What??)

Conclusion

Both are ok and can be used interchangeably.