Well, I have to disagree with you.
The IUD is certainly scientifically based as well, women didn't just start shoving things up their uterus and hope for the best! (I'd like to say this is 100% true, but there are the few stories you hear of women shoving potatoes and other things up there as birth control as well. However, I am choosing to pretend that this must be before ladies were more sexually liberated and educated)
First point: some IUD's are chemically/hormonally concocted. Just like the pill, they release the hormones into the body to control the cycle and thickness of the lining. They just do it in smaller doses because it is directly next to the affected area, and its over a longer period of time (5 years vs. 24 hr or 28 day cycles)
But, that being said, IUD's that are not hormonal still have a chemical-reaction aspect because of the copper. WebMD sums both kinds up nicely: "Both types of IUD prevent fertilization of the egg by damaging or killing sperm. The IUD also affects the uterine lining (where a fertilized egg would implant and grow)."
If I were a dude, and I hated babies (Or you are like me, a lady who hates the idea of having babies) - I'd go for the IUD. Its more effective, partially because of the close-to-home approach, and partially because you never have to make sure you are timing it right (even taking your pill a couple hours off can affect the effectiveness of hormones). IUD's help the lady friend be less hormonally crazy (bonus!) AND if somehow your lady friend does get knocked up, its an automatic abortion - it is nearly impossible to keep a viable fetus with the IUD.
Now, this does start to enter into a grey area ethically, and if you are opposed to abortion you may (or may not) be against the IUD for this reason. But that is a whole other issue that I don't think really warrants discussion here.
But in any case, rest assured that they IUD's are also created (and I can also vouch for, inserted) by scientists/doctors/nurses in lab coats!
Wanna see pictures?
http://www.webmd.com/hw-popup/intrauterine-device