Hello, as a layman with no technical ability or knowledge , I'll give my short view of the two. I have handled, viewed and used many examples of both, over the years . The 400 series are in general delightful, pleasant and have a lovely feel. Reliable and very nice . The 700s are workmanlike with average looks and fairly lifeless ,again reliable. Pound for pound and all being equalI would opt for 400 without doubt. Pigs ears and silk purses in both series of course. Regards