Actually 4 looks better than 3. The character designs are worse, but in terms of detail it's lots better.
As for the features, yeah it was done by a different team. There are two Suiko teams. 4 was headed by a new team and a new director. When it came out, there was a big 3 backlash by a lot of 1 and 2 fans, so the makers of 4 tried to go back to Suikoden's "roots", and ended up fucking up everything.