When I changed my fan belt one year ago, I found the new one (Dayco A/C + ACE PQS101510) was longer than the old one, so it was easy to undo it. I asked the seller, they told me they had no problem with hundreds of buyers. Sometimes I can hear squeak noise on start or stop, but no problem in drive. My disco. has A/C + ACE. First, I wonder why new belt has different size (around 5 cm longer or more), next, if it would damage engine.

I put a Dayco one on when I renewed the tensioner and that squeaked. Changed it for a Conti and cured it immediately.

I had the same problem with Dayco. Definitely longer than the original one (and seems thinner). When I used it I also had squeak. I removed it and use the old one which is still in good condition and put the Dayco as spare.
Maybe I will also try Conti...

Conti belt is the only one worth fitting