Long answer:
Go Mechanical, it is a lot easier to go B1(mechanical) to B2 (avionics) at a later date if you decide to go licenced than it is to go B2 to B1. B1/ mechanical covers a much wider variety of systems & technologies, and still covers a hell of a lot of electrics.
I was Mechanical in the RAF & now hold B1 & B2 licences, being dual licenced opens a lot of doors for you as you have no restrictions in signing off any defect, and modern aircraft as mentioned earlier are far more electronics based, so it makes sense to cover all the bases if you can.
Short answer:
Do you ever look at your dog and think "hmmmm?
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