I don't know about the 2013 sails as I haven't used those. The 2014 S1 is a pure wave sail... meaning if you hold it flat into the wind in a neutral position it will flap like a bitch... but that's just what a pure wave sail will do. That said, I am positively excited about the S1. Did I mention it's stupidly light? For heavier riders like myself it won't have the same power as an Atlas. But I found in very light wind the additional weight of a cross over sail counter acts the power gain. Once you get planing conditions I would switch to using my Combats anyway.
Sails like the NP Atlas are a lot more free ride oriented these days, especially in the bigger sizes. Don't get me wrong. I think the Atlas / Alpha is / was a great sail. But it's different in feel to say a Blade or Combat let alone S1 or The Fly.
I guess the closest Severne has to an Atlas is the Gator. I am not surprised you liked the Gator given you really seem to dig the Atlas.
I think with the arrival of large volume wave boards we will also see a shift in the way people buy sails. In the past I would have always bought a full quiver of sails from 6.2 right down to 4.2 in the same range. These days I am not so sure that's the best approach.
For example for me I have worked out that for ultra low wind wave sailing on the Australian East Coast I prefer a super light rig with a wave board that turns well but has a decent amount of volume. On the flip side when it's windy I prefer a setup that is neutral in feel and stable in jumps. Rig weight at that stage is secondary and durability to me is more important... hence why I went the Neil Pryde Combat HD route. I think you could drive a car over that sail and it would still survive.
I'll give you a shout next NEer I am down in Gerroa. Have a go on the 2014 Severne S1 5.6. I think it would make a great addition to the 120 liter OES board you got on order.
FYI, I am not a Severne fan boi. Quite the opposite. I love Neil Pryde sails. I think they make some very solid sails, albeit a little on the heavy side.
Then there are a couple of things I would improve on the S1 as far as build is concerned. But you can't beat that sail for weight. If a light weight sail is what you are after you have to look at the S1. I am actually surprised they are not pushing this more in their marketing.
The Enigma mast they lend me is very light as well. Very similar in feel to the Neil Pryde XCombat / FX100. Fast and responsive flex and in both cases big price.