My best friend in HS was a Mormon. Later came out as gay and died of AIDS at 26. His service was held in a fully packed LDS church and he was surrounded by his family at the end.
That is what tells me of the critical differences between the two. Religion wise, they are both strange, I know what both believe and while the LDS has nutty doctrines, they are more of a lifestyle religion(the religion promotes family and life), where the JWs are about making sure no one does anything that doesn't promote the religion. Family is an accessory, and an unecessary one at that.
There were some wrong things earlier said about LDS. Women get callings even if they don't get married before getting out of college. Women can serve missions, too, but aren't expected to as the young men are.
Family planning, as long as it isn't an abortificant(?) is now acceptable. Premarital sex, not. People can come back from it easier than JWs, and it is kinda a job to get excommunicated as a mormon. You have to really piss off the powers that be. Which is why there are so many "jack" mormons. (I'd be the one drinking coffee unrepentently!)
No joke, the theology is whacked and probably more so than the JWs.(coffee???!!!) That racism was a part of it while slavery was unacceptable is odd, but I've seen both of them up close and personal, and if I was to hang around LDS or JWs, I personally think LDS are generally a lot nicer, kinder and more fun. I also see them helping others, LDS or not, Tithe payers or not. I don't see JWs helping anyone, not even each other, mostly. Their religious lives(LDS) are built around serving each other and helping others and that says more than their wacky theology IMO.