The pool is probably safer. Don't use the pool filter (remove it completely, since chlorine can get trapped in the lines). Declorinate everything thoroughly. Add a pond filter and aeration. You can easily put a net over a raised pool. Toss some pool noodles, balls, or other floaties in under it to keep it from going under the surface (you may need to zip tie them to the net to keep them in the center). Full body length foam pool floats would also provide shade and protection from predators. Keep in mind that the new water will have to cycle, so that's stressful on the fish and you may lose some during cycling. I recommend adding a dose of Seachem Prime daily, or as needed based on water parameter tests using the API master kit. I'm assuming since you're experienced, you know about nitrogen cycling in ponds. If not, I can post a few links. Adding beneficial bacteria can speed up the cycling process. Perhaps it may be possible to pump water from the pond at the location into the pool once it's been drained, cleaned, and declorinated? The pond water wouldn't need to cycle once in the pool, but you could introduce diseases into the pool by using water from the existing pond. It's a coin toss on which is the better solution. Something to think about.