The Quicksilver does have the odd issue on warranty (every boat you ever buy will), maybe a few more than it's fair share. More importantly the 500 is trying too hard to be one or two feet bigger and it doesn't do it.
This is not my words, but those of a Quicksilver dealer when discussing the best and worst boats we had been lucky enough to drive.
"It's one of the worst boats on the water, feels so dangerous and unstable, just lie a bathtub with a cabin on it".
If you upped your search to the Quicksilver 580 you would then have a reasonably stable little boat. Still the same issues as many others, but usable.
The Warrior 165 is the "designer brand" of open cuddy fishers and is a reasonably built, pleasant angling boat. Good on the water, benefits from trim tabs, fairly quick. You will have little onboard comfort and you will take a bucket of water in the face from time to time, particularly in a cross wind when spray is whipped around the forward running rear edge of the cuddy.
The Predator will be a very similar boat to the Warrior and will have the same pros and cons.
The Merry Fisher 530 does actually work well as a Pilot House as the actual heavy superstructure is kept to a minimum up top. This prevents her being any less stable than similar open cuddy designs.
She will be fractionally slower than the other two if fitted with the equivalent engines. Expect a 50Hp 4 stroke to provide mid / low 20knot performance and a 70Hp (maximum) to provide close to 30 knots. The hull is a good sea hull. She benefits from having a little keel running to two thirds of the way down. This provides excellent steerage at low speeds and also helps the boat drift at a sensible angle rather than spinning like many full planning hulls.
Whilst not being a gin palace, she certainly does have a higher level of trim than the other two boats and is strongly built and fitte out. If you do get a problem, you do have a strong dealer network more or less nationwide to look after you to.
I say more or less becuase at Christmas, your local dealer went into liquidation after the directors were found to being a little less than honest. I don't think Jeanneau have reappointed a dealer for North Wales yet so you will need to find one that you feel you can trust and that you are comfortable with.
....I just happen to know a good one that also has a 530 in stock right now, but I suggest you ask Afishionado and others on here as to whether or not he is any good and true to his word.
Happy hunting
Tom