I bought and shot 3,000 rounds of loose, "recycled" IM ammo of mixed makes a couple of years ago. Never had a problem for just blasting ammo, but there were lots of horror stories during that time of problems and about the storage and cleaning methods used for this ammo. Story was that this was range and/or patrol ammo that cycled through magazines many times and then stored in 55 gal drums for years at high temperatures in metal buildings. After import, it was rumored to be acid washed in concrete mixers to clean up. Evidence on the ammo I had suggested that these stories might likely be true. At that time it was $100/1000.
I would be tempted at the $100 price again, but would go for the boxed ammo for the relatively small difference you quote. You will sleep better with the boxed ammo if you are the worrying kind.