I grew up with a very head strong castrated springer dog that had the heart of a lion. His previous owner wanted rid of him as he was "untrainable" so we gave him a home at 2 yrs old. Several dead chickens later and a few loaves of bread stolen off the kitchen table and we managed to educate him with some basic manners. He once did the 3 yorkshire peaks and could have kept on going until he dropped.
He used to run alongside the quad bike and never ran out of steam. He never could be trusted in the beating line but it didnt matter for the type of shooting we did with him. There was one occasion we thought we had lost him for good when he tried to retrieve a duck that came down into our local river in full flood. Amazingly he came back 20 mins later with the duck in his mouth.
At lambing time we had to keep a close eye because he was known for retrieving a lamb or two. Fortunately he was soft mouthed.
Another weakness was his obsession with food.
Aged 12 he pinched some pork pies in clingfilm which caused a blockage in his guts and he ended up losing 6" of his gut.
A year later he ate a peach stone which got to the the narrowing and caused another blockage. He then lost another 6" of gut.
At 15 we said our good byes but memories of the lion heart stay with us.
Now Ive a family of my own and my first dog you guessed it was a springer. She's 4 yrs old now and probably the most loving natured dog Ive encountered. When she rides on the quad she constantly nuzzles me for a hug. When im working her its best to let her run some steam off for 30 mins before I can get any sense out of her. She works through brambles like a machine and visibly suffers the next day after a days beating. But she cant contain her excitement when she sees the guns arrive on the next shoot day.
Hopefully this next season I will let her have a litter.
Overall they are fantastic flushing/beating dogs when your labs just tend to prance around the bushes. I would agree the most important training aspect is recall and if your wife wants to have good control of a spaniel then she would be best doing the training and not be afraid to be tough.
My bitch's weakness is her retrieving but I can live with that as she makes up for it with her flushing.
Springers also generally seem very tolerant of other dogs and humans
good luck with your new companion