I had clamp on ones for a while.
Pros: Cheap,
Easy storage.
Great for light stuff.
Cons: Eventually (if, or when?) you push the limit you'll bend the bucket edge and give it a nice "perma-smile, forever altering ability to cleanly scrape a paved surface with the bucket.
The bolt clams will make indentations in bucket - not a big deal.
Eventually bend the bolts that clamp them on, which makes getting them off "fun" (not), and
Without the "stabilizer bar" that links one to the other, they'd have a tendency to rotate on the bucket (that is, not be perpendicular and stick out straight forward) when being used "rigorously".
Harder to see fork tip from tractor seat, as bucket may block vision depending on their length. Yet longer forks increases leverage footpounds, increased chance of bending, lower lift capacity at tips, etc..
Note hood may block vision with ANY type, depending on fork length.
Does tractor have a seat safety switch if you need to stand?
Eventually I bought a good pair of forks with their own quick connect frame from one of the advertisers to this site and was glad I did. As useful as they initially were, I sold the clamp ons.