Also chiming in to recommend letting your wife pick out this awesome gift. In fact, you could make it a surprise trip, if you have a dealer who you can visit that sells multiple brands.
Now, you are going to get a lot of responses here of "I love my XYZ", and while they're trying to be helpful, a sewing machine is a very personal choice. Does the user find the controls intuitive or confusing (or worse yet, intimidating)? Is the sound like white noise or fingers grating on a chalkboard to the person using it? One sewist's Chevy is another's Ford.
Kind of like golf clubs (how does it look at address? How does it feel at impact?) Does the machine inspire confidence or create insecurity? That is a personal thing.
So please, let her pick.