I paddle a Swordfish S, but used to paddle an Elite, and have paddled a friend's Elite S a couple of times.
For the stuff that I do (more or less constant downwinds in choppy water), I'm bullet-proof in the Swordfish S and have several of my best times, including my best two times in the Swordie - so I have no feeling of FOMO when it comes to "elite" level boats, except in the most flat of races - which occur very seldom anyway.
My buddy who paddles the Elite S swears by the elliptical rudder - says the boat tracks straighter and, at low speeds, turns better. If you're a super-elite hero paddler who can turn 360 degrees by leaning at just the right time, then no, perhaps you could stick with the shark-fin rudder, but in my observation, those paddlers are few and far between and have paddled all their lives... by far the majority of paddlers will primarily use their rudder to turn.
On the Swordfish, I use a DK rudder from Don Kiesling in the US - it's even more effective than the elliptical rudder and I recommend it to the hilt. The best thing about the rudder is that it keeps the boat super-straight... Even on the flat, I think it increases my speed - perhaps by reducing the amount of fish-tailing when I'm really paddling hard.
You never want to use a lot of rudder at speed - as your friend says, an efficient rudder will induce roll in the boat if you stamp on it when you're moving fast. The shark-fin rudder is almost useless at speed anyway - the meat of the rudder is behind the pin, so it becomes harder and harder to turn, the faster you're traveling. It also has a horrible-shaped, flat cross-section, so it stalls very easily. The elliptical rudder is easier to turn at all speeds because it's balanced - but that also means you can over-use it at high speed and induce roll. The elliptical has an airfoil cross section so it stalls less easily than the shark-fin.
The DK rudder has the best of both worlds, being super-effective, but also balanced so that it does tighten up a little at speed - so it's difficult to over-use it.
So IMO, it's definitely worth putting a more effective rudder on the boat - try it for yourself. And if you can, try the DK rudder, it's awesome. Get hold of Don at This email address is being protected from spambots. You need JavaScript enabled to view it..
Rob
Currently Epic V10 Elite, Epic V10 Double.
Previously: Swordfish S, Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...