Is the Roland FP-60X worth the extra $450 over the Yamaha P-225?

It depends on how you'll use it. If you sing along with your playing (mic input), need flagship-grade action (PHA-4 with escapement), or want bigger speakers for a living room, yes — the FP-60X earns its price. If portability, modern design, or pure value matter more, the P-225 is the smarter buy. There is no wrong answer here; these pianos target different players.

Which has better piano sound?

They're both excellent but different. The FP-60X's SuperNATURAL Piano is modeled and warmer, with smoother dynamics. The P-225's sampled CFX Concert Grand is brighter and cuts through mixes better. Through the FP-60X's more powerful speakers, the overall "room sound" is fuller. Through headphones, the P-225's CFX sample is arguably more impressive. Both are flagship-derived engines.

Can I gig with either of these?

The P-225 is vastly better for gigging. At 11.5 kg it's easy to carry, and the CFX sound cuts through a band mix. The FP-60X is technically portable but at 19.3 kg it's a two-person-carry piece of gear. For dedicated stage use, consider a stage piano under $2,000 instead — they're designed around live performance.

Which is better for a complete beginner?

The Yamaha P-225. It's lighter (easier to commit to keeping out), looks modern (lower "nagging to practice" resistance), has excellent Smart Pianist app support for self-guided learning, and the $450 savings can go toward lessons, a bench, or a sustain pedal. Upgrade to the FP-60X (or beyond) only after you've confirmed piano is sticking.

Do I need a sustain pedal or stand with either?

Both pianos include a basic footswitch-style sustain pedal in the box. Neither includes a stand. Budget $60–$120 for a sturdy X-stand or Z-stand, and $30–$60 for a proper half-damper-capable sustain pedal (especially worth it for the FP-60X's continuous damper response).