Really, a three-year-old bike he will outgrow rather quickly. My son outgrew his, size-wise, by about 5 1/2 years old so I wouldn't spend a lot of money on it. He actually got the bike from Santa at 2.7 years and was riding without training wheels before his 3rd birthday, in May. If your son's large motor skills are that good, you will be extra-busy this May!!!
My son's first bike was from Toy's R Us. It was some off brand (even places like Sam's Club and Costco carry cool boys bikes in season). He was always on his bike and surprisingly, it lasted for a long time (just tossed it out last year - he had high hopes of painting it and keeping it as a second bike - he's going on 11.) We bought a second bike, for his birthday, just before 1st grade.
Toy's R Us (Schwinn) aren't like the old Schwinn's. My daughter bought a Schwinn bike there, when she was going into 3rd grade and it lasted only a couple years because it just fell apart - very disappointing. Her bike before that was a Huffy and she just outgrew it.
I'd go for the color and fit - I love the fact that it's a "baby" present to the big brother! My daughter was 3 when my son was born and the "baby" gave HER a present, too. Not quite as big but was very meaningful. Now, they are 13 1/2 and 10 1/2 and maybe that's why she adores him to this day! Great age difference. Congratulations!