Absolutely no sides.
MSM will make your hair and nails grow in thicker, stronger, and have an all-around better appearance.
MSM will also give your skin a healthy glow, and maybe make the white's of your eyes whiter.... at least, in my experience it happened.
L-Arginine is my favorite... 2 or 3 grams a day will give you great sexual energy, better strength, leaner body mass, and it can possibly help with your hair... In my opinion, 2 or 3 grams of L-Arigine for at least 6 months will have a cosmetic difference in your hair... It will make it stronger, thicker, and healthier.
They are both safe to take, but as always, if you're taking medication, or have other conditions, you should check with your doctor to see if it's okay.
Vitamin stores offer the most for the cheapest... although, Wal-Mart sells really cheap MSM.