if you love colors, go for the 5C. Don't get an iPhone 5, they're probably gonna stop getting software updates after iOS 10 because the original software on those phones was iOS 6. If you want speed, spend more on a 5S.
I've always thought they were a pretty slick looking phone. Iphone 4's seem to get worse as time goes by, from battery to speed. However I never had any problems with my 5 or 5's.
yeah the design and aesthetics is definitely their best. Too bad the specs are a bit outdated for me and I do like a bigger screen so I had to upgrade to the 6.