I currently have a S3 and want to upgrade. Should I purchase the S5 OR S3?
I also have a S3 currently, but I will not buy S5. Because it is so ugly, then the specification of S4 is not inferior to S5, S5 only adds fingerprint technology which is useless. What's more, the price of S5 is 200 higher than S4. It is definitely that S4 is more cost-effective than S5. However, why do you only focus on Samsung, I consider that Sony Xperia Z2 is the best choice for you, or maybe I can recommend other smart phone if you want.
It's the OP's decision about which one is uglier. I think the S4 is uglier.
I think for the Snapdragon 801 (versus the 600), the fingerprint scanner, improved screen and camera, and just having a newer phone with better resale value is well worth the $200.
You won't regret spending a bit more and getting the S5.