They are both basically the same boat. Same hull, same engine, probably same basic performance and sailing characteristics I'd imagine. Here are some purely subjective opinions. Some things we've noticed:
We like the interior treatments in the 336 a bit better, with things like the molded composite galley sink and the ash planking in the main salon. It appears that Hunter was looking for ways to lower costs on the 340, and the interior finish treatments show it.
It can be a bit difficult to move forward on deck on the 336 because of the lower shrouds, you have to do a Tarzan swing around them. They were rearranged on the 340 to make it a bit easier to get by them, but for some reason they also deleted the forward grabrails, which seems to negate the gain from moving the shrouds.
I don't imagine boarding seas are much of a concern, but I've never liked how they eliminated the line locker on the 340 and lowered the bridge deck. Yes, it makes annoying squeaks when you step on it, but we like the large line locker below the companionway on the 336 and the fact that you'd need a tsunami in the cockpit to get any downflooding.
We've gotten used to the compromises on the pedastal that come from mounting the traveler there. For example, the engine control lever is just wrong on the 336. It's mounted with neutral facing forward, and you have to push it down for forward, pull up for reverse. My wife always has to ask "which way do I push it?" when she turns around and tries to back down, because it's not intuitive. The vertical arrangement on the 340 seems more logical and more what everyone is used to. And as the previous poster mentioned, it's hard to mount electronics on the 336 pedestal. We've been fine though with the instruments above the companionway (best place for them actually) and a Garmin Oregon GPS on a RAM mount on the pedestal grab bar.
The pedestal mounted traveler on the 336 is not of much use. I've taken to using the mainsheet if I need to dump some air, instead of the traveler, and that's not really a good technique to use. I do have some concern about what an uncontrolled gybe in high winds might do to the pedestal, although it does appear to be pretty stoutly built. I know there are some 336's with the traveler mounted on the cabin top, so that might be a better arrangement to consider.
And here's where I'll admit that I could be completely wrong, since I'm no marine engineer (computers are my thing) but the boat was designed to be driven by the large, full roach main sailplan on the 336. I know that some 340's (without roller furling main) have basically the same sail, and would probably sail the same, but I have to think that the changes necessary to add the roller furling mainsail throws the balance of the sailplan off some. I think maybe they made the mast a bit taller on the 340 to add some more drive to the main? Anyway, the 336 is a sweet sailing boat. She'll glide along at 5 knots in 8 or 9 knots apparant. We've been out in 20 knots apparant on a close reach with a single reef, and the boat is so balanced you can let go of the wheel. Maybe the roachless main on the 340 with roller furling is equally balanced, I can't say not having sailed one.
A few things not to like about both boats. For some strange reason, the designer molded channels topside that direct deck drainage from rain storms directly across the head and aft cabin opening ports. Forgetting to close these ports in even the lightest shower can pour gallons of water into your boat. And they constantly leak, because it's virtually impossible to keep them water tight enough to basically handle being submersed whenever it rains. The propane locker it too small, requiring the use of hard to find 4.25 lb propane tanks (best deal is at Lowes.com). And the anchor locker is too small. Mounting a windlass can be a challenge. Enlarging the battery bank by adding another house battery usually results in one battery box being fixed to the removable access panel above the holding tank, which means it's not really fixed at all and will tumble in a large heel. And for some reason, ours has always had a starboard list, which seems aggravated by the fact that all the easy to use storage is on the starboard side, so that's where all the "stuff" ends up.
Bottom line is that in my opinion, the boats are close enough that I'd let price dictate. Go for the better deal. If they're close in price, then I think you'd be happier with the newer boat provided the condition is equivalent.
