In order to avoid pointless discussions certain assumptions have to be made. Firstly, I assume first that you are looking at
purchasing a boat new. Secondly, I assume you are cruising, not
racing, and therefore require a certain degree of comfort. Ergo, you are going to load the boat up with 2-3 tonnes of
gear.
The performance of these boats are well documented as detailed above. My view, having looked closed at the new
Lagoon 420S is that it compares well to the Helia 44 and the
Lagoon 450S is huge, so the
Lagoon 420 is more of a competitor to the Helia.
My Helia has now performed over many miles and conditions at around 170nm per day, and properly sailed and fully loaded with about 3 tons of
gear you can get it moving at 10 knots over a few hours in favourable conditions. Having talked to many Lagoon owners I suspect performance is similar.
I have been researching a faster boat for around 2 years. The problem is that after having a Helia or Lagoon you want (or more correctly your other half wants) a boat of similar size, comfort and quality. In order to achieve this in a performance boat you need to go to 50ft +. If you are prepared to sacrifice size, comfort and quality in return for speed then this is a different story.
This pick of the boats in my view is the O51, but Factor has also mentioned other 50ft+ boats that are also applicable. The penalty is cost. You will be paying at least 50% more in cost to achieve this outcome.
What do you get for the
money. Remembering, that in comparing apples to apples you need to consider the boat loaded up with say 2-3 ton of gear. Typical performance boats will in all conditions achieve a 25% improvement in average daily performance (let us say 200-220 nm pd), and sailed well will achieve 12-15kn optimal performance over hours.
I hope this helps.