Use a supervised guitar trial to assess basic playing position and response, then separate learning questions from setup work that belongs with a qualified technician.
Compare piano types through an ordinary practice session, accounting for sound, touch, placement, upkeep and the actual model rather than treating either category as a universal answer.
Separate keyboard range, physical key size and touch response, then try the instrument against your intended lessons and the space where you will practice.
Compare a rental and a purchase over a realistic learning period, including the actual instrument, essential accessories, service arrangements and the terms for returning or keeping it.
Choose a first instrument by balancing the sound you want to make with practice access, household constraints, instruction and the complete setup cost.