I have Wellies, Ameruacanas, and Marans.
These are from a single breeder, so it is a small sample size and they are only about 4 months old.
The Wellies were my target breed with some of the others thrown in.
I have heard the Welsummers are flighty. In fact I know one woman who got rid of hers because she said they were so flighty. I have found this is not true.
Of the three, the Welsummers are the most intelligent, friendly, and vigorous. They grew the fastest, feathered out the best, and had the best appetite. They seem to spend the most time grooming and have a more tidy appearance.
They are the first to learn how to get in and out of the coop, what treats are, how to eat out of your hand, etc.
Sorry to say it Marans owners, but the Marans I have are dumb by comparison. The Marans lay back, and seem to be the last to realize I have shown up with treats, have the hardest time getting in and out of the yard, etc.
My daughter's job was to handle all the chickens every day and many times she would do it more than twice a day. So, all birds were handled equally and often when they were young. I can pick up all of my Welsummer hens and some will come right up to you and talk to you when you pick them up. They are definately a "tame" breed and are comfortable around people. Type -wise they are very uniform. The hens all look the same and it has been hard to pick out what rooster I will keep.
The Ameraucanas are cool, but freak out a little when you first pick them up. They like to be around you, but are not as tame. They are smaller, less vigorous growers, but calm and inquisitive....kinda cute little guys.
The Marans by comparison, are not friendly at all, hate to be held and are the last to come to treats. Basically, I have to catch them to hold them. The Marans, however, seem to be more weather hardy and are the only ones that stay out in the rain and foul weather. This is is something important for me to watch because I live in Alaska.
On the other hand, the Welsummer roosters are more roudy and dominant over the other 2 breeds. They crow more, fight more, and pester the hens more. Not mean yet, but definately more like a teenager in heat. Marans and Ameraucana roosters seem a lot calmer.
Welsummers seem to be typed more like an egg layer as opposed to dual purpose. They have not put on much meat yet and the roosters are bony and tough...better suited to soup. The Marans grow a little slower, but feel more heavy and meaty. I think they would be a better dual purpose breed. The Ameraucanas are smaller and grow a lot slower.
I'm obviously biased towards the Welsummer breed and like I said, I'm judging from a small sample size and my birds are still young. I find Welsummers to be intelligent, energetic, and friendly to the point of being a little roudy.