I flew B737-700 before and after installation of winglets. I never detected the slightest difference in any handling, and they were quite large- 2 metres, I believe. Some of my colleagues claimed they did detect a difference, but I think it was more in their imagination. I also flew B747s early models without winglets, and the -400 with. Again no difference you can notice. We used to occasionally fly the -400 with a winglet removed- absolutely no difference. It's like filling your car with standard or super petrol- absolutely no detectable difference so take the cheaper one! Though there's always smart ones who claim they can feel the difference!