In terms of recovery time and pain which is better -- a knee reconstruction or a knee replacement?

Reconstruction: As a general, but never 'always' response. See prior answer for details on this. With knee replacement, intense pain may resolve in few days, full pain weeks-months; full recovery time generally 1-6 months.

Both: While a knee replacement is often quite painful, this usually resolves over 6-12 weeks and one can return to normal activities. A 'reconstruction' can mean many things, but typically waiting for tissues to heal takes much longer before full recovery is achieved.