Spanish in adjective clauses

[laepelba]

I'm still working through some of my issues with the subjunctive in adjective clauses. The workbook that I have seems to me to have insufficient explanations on this topic, so I'm reading some articles online.

In one article, I found the following two sentences:

Escoge la clase que más te guste.
Escojo las clases que más me gustan.

I'm a little fuzzy on the reason for using the subjunctive in the first sentence.

The article gives the following translation for the first: Choose whichever class you like best. Does the subjunctive, then, imply the "whichever"? Or would the sentence be better written as Escoje cualquier clase que más te guste.??

(I definitely understand why the second is indicative.)

Thanks for any suggestions you can offer!!