Lots of valid points. The modern trialing springer is a different animal then in the past. The modern spaniel is smaller and faster and the trials are set on ground that is laced with game. The modern trialer will prefer a spaniel with less drive(due to the amount of game on the trial site) and a spaniel that is of a soft temperant that can be trained like a robot.
the spaniels that won in the 70's and 80's were dogs that would hunt ground all day even if they came across very little game as they had very high drive. These dogs would not do well in a modern field trial and vice versa.
In ireland there are pockets of spaniels that are still big boned and strong, in recent years these dogs are been bought by Uk breeders to introduce size back into the breed.
Cockers are still relatively untouched in there breeding lineage as they have only recently become popular in trialing circles. There is talk that openshaw is now concentrating on trialing cockers more as he knows the Ess gene pool has been damaged beyond repair.
So there is an example of 2 dogs from two different back grounds that can work together with some owner effort put in.
It is a pain in the hole when you look through donedeal and every set of pups sire is hattonswood broc or skronedale romulas, the interbreeding in a few years will be a joke in irish spaniels.