As you can see from my signature, I've had a few of them over the years. I also did test runs in the SV2 208 and 228 before settling on my current 226 Seafarer.
1. The old 204c, while a very wet riding boat in bigger seas, will handle a 1 ft chop very well. The hull has a mind of its own and does not respond to trim tabs. It was the most stable fishing platform of all of them. It also has the widest walk around channel and you can actually fish from the bow it it isn't too rough. You pay for the wider walk around by losing some space in the cabin. You sleep with one shoulder under the walk around. Not good if you turn over a lot when you sleep. I spent many nights on that boat, but I don't think that I was ever able to get to sleep. The old 204c weighs at least as much as the newer 226. The listed weight of 2400 lb was not correct.
The boat is a whale and solid as a rock. Unlike the SV2 hull models and even the pre-SV2 Seafarer, the 204c will drift sideways into a tide rip. This lets you fish the side of the boat rather than from the stern. The SV2 hulls drift bow first into a rip. The 204c was also the best handling boat during docking maneuvers. Tuck the bow in 45 degrees or less, turn the wheel, put the engine in reverse and the stern will pull parallel to the dock. Try that with an SV2 hull and the bow will pivot out.
2. The pre-SV2 Seafarer was a very well laid out boat. As everybody says, the extra 2 ft is very nice. You can fish 4 people unlike the 204c where 3 fisherman was the max. The hull rides much drier than a 204c, but it will pound in a short 2 ft sea. The drop down transom splash gate was a great feature for diving and getting in and out of the boat from the stern.
3. The SV2 208 is an excellent riding hull, almost as good a ride as the SV2 226 or 228. The cockpit seemed smaller than the 204c, but that could have been due to the fish boxes and wells under the helm seats. It's a very versatile boat and is easy to launch and retrieve. Just a bit too small for me.
4. The SV2 228 is the best laid out for fishing and diving. Everything seems to be right where it belongs. The stern live well is really nice if you use live bait. It takes a bit to climb over the transom to get to the swim platform/bracket to get in and out of the boat. While the ride was good and dry, I don't like the way bracketed engine boats handle in big seas. They like to go fast and I found the minimum planning speed to be about 27 mph in a good chop. The transition to running just off plane was dramatic. They tend to yaw slightly in a following sea unless you are firmly up on plane. Both 228s that I tested also has a slight tendency to porpoise. This could easily be corrected with the tabs, however.
5. I ended up with a 226 because of the rough water ride characteristics. A salty old guy up in the Panhandle told me that he liked the ride of the 228 except for when the seas got really nasty. He suggested that the 226 ran better off plane and was generally a more solid ride in bad seas. I found that to be exactly right. With the right prop, you can keep a 226 on plane at 22 mph unless the seas are really bad. They also ride solidly in a bow up conformation when slogging off plane. The off plane handling characteristics are more similar to my old 204c.
Unless you can find a pristine or recently restored 204c for a great price, I would also suggest going with the SV2 hull. The smoother and drier ride more than makes up for the low speed prop walk and funky docking characteristics.
If you have specific questions about any of the models discussed here, send me a PM.