I've flown both the -100 and -300 versions of the 737, and despite the 20 year age difference between the ones I flew, they were still very similar aircraft. The nav systems were vastly improved in the -300, but they were still basically the same aircraft from a pilot's point of view.
In between the 2, I spent several years flying BAe146s. Dreadful aircraft compared to a Boeing, especially from a performance point of view BUT, a nicer place to spend the day with a roomy flight deck and nice big windows.
Now I've been flying the A320 for a year and a half, and it is the easiest jet I have ever flown. It took a bit of getting used to, but now I would never choose to go back to the 737. From a comfort point of view, there is no comparison, and at the end of the day, that is the important thing for me. If I have to spend 8 or more hours in the flight deck, give me an A320 any day.