Learn Spanish (Latin America): Mientras menos simetría tiene la cola, más problemas hay. - The less symmetry the tail has, the more problems there are.

Both cuanto menos... más... and mientras menos... más... are correct and commonly used to express proportional comparisons. In Latin American Spanish, using mientras or even entre for this correlative structure is extremely common and perfectly natural.

Why is tiene in the indicative rather than the subjunctive?

The conjunction mientras only requires the subjunctive when it refers to a future or hypothetical condition, where it usually translates to 'as long as'. Because this sentence describes a general, established fact about the tail rather than a hypothetical scenario, it uses the indicative verb tiene.

Could we use entre menos instead of mientras menos in this sentence?

Yes! In many parts of Latin America, particularly in places like Mexico and Colombia, you will frequently hear entre menos... más... used interchangeably with mientras menos or cuanto menos. They all mean the exact same thing.

Is it mandatory to put the noun simetría directly after menos?

Yes, in this type of comparative structure, the noun being quantified must immediately follow menos or más. You cannot separate them by putting the verb in between, so a phrasing like mientras menos tiene simetría would be incorrect.