Feel and rhythm
Manual typewriters give a tactile, deliberate rhythm that many writers love. Electrics offer lighter touch and uniform impression with less fatigue over long sessions.
Reliability and service
Manuals have fewer things to fail and can be serviced indefinitely. Electrics add motors and rubber drive parts that need periodic attention but remain very serviceable.
Portability
Manual portables travel anywhere and need no power. Electrics are heavier and tied to an outlet.
Print quality
Electrics, and Selectrics especially, produce very even, professional print. A well-adjusted manual is close, but character darkness will reflect your touch.
Cost and availability
Good manual portables remain plentiful. Quality electrics are available too but benefit from a bench check before purchase.
Both types can be a joy to use. If you are undecided, visit the shop and type on a few machines before you choose. Related service: Carriage and Escapement Repair.