I've played Runescape since it was out, on and off over the years of course.
I've played WoW for about a year, started seriously in the last 2 months. Right now I am enjoying it a lot, especially cataclysm which is actually a challenge rather than faceroll Wrath.
In RS, you start a lvl 3 character. You grind skills in the same locations, clicking the same objects for hours and hours on end. After spending countless hours grinding each separate skill, you finally reach high enough levels to do PVP, or kill some end game bosses in GWD or corp beast etc. Sure you can try out the other skills and new content like dungeoneering - which turns out to be a massive grind just like every other skill. There are limited available armours and weapons. Once you have your bandos set and one of the very few decent shields/weapons, your cash pile sits there ready to be consumed for more skill grinding, or to save up for rares or merchanting. PVP is complete RNG luck most of the time. Anyone who argues that RS PVP takes skill these days is an obvious troll. With autocasting and idiots like dclaw rushers filling pvp worlds, this game has gone to the shitter. QQing when you die and lose everything then starting again to get back your items, is a simple rinse and repeat cycle that is far from entertaining. Then again, I never had the patience to grind back lost gear, so I never PVPed seriously. Yes there are good things like RS being a browser game, meaning you can play anywhere. And sure it has f2p, but then again that's why the WoW community tends to be of an older age group.
RS graphics have never been a strong point, and they still are not comparable to WoW. I for one am influenced heavily by graphics - after all, the better the graphics, the more of an immersive experience that the game provides, at least in my opinion. WoW has better music, graphics, default UI, and almost complete customisation that RS lacks.
PVE wise, WoW excels far beyond what Runescape has ever provided. And it truly lives up to the meaning of an MMO - working with other players in a group. Wrath was complete faceroll, but with Cata now out, dungeons are a challenge and require competent team players, which makes the game very interesting, even if you aren't hardcore. All you need is sense. In Runescape it's more of a solo thing in my opinion. Also there's the complete lack of a dungeon finder system that WoW now has, and you still find yourself searching for a decent clan or group in chat to take down corp beast or to do other pointless shit then get crashed by some fags from another world. GG loot.
And to whoever said in RS you can choose between 3 combat types but not in WoW, you CAN do that and far more in WoW. Ever heard of dual spec? Each class has 3 different talent trees, especially for the hybrid classes like paladin or druid which can play either dps, healer or tank. And you actually need a lot of skill to play your class well. Plus there are 10 classes with specs each. And somehow that doesn't completely trash the 3 class choice of RS?
PVP wise, I personally prefer to keep my items on death, and to have a variety of stuns, gap closers, dispells, range/melee abilities and otherwise. An actual rotation, or a need to modify that rotation based on situation, if you will. Some might even call it skill. Sure beats sitting on the wildy edge and running in and out hoping that your GS or claw specs 2 hit them.
Since just prior to the release Cataclysm, WoW changed dramatically. Leveling 1-85 is now, for lack of a better term, fun. Quests have all been reworked, as have item rewards and the general experience is amazing. Try it if you are still doubtful after having facerolled through Wrath then QQ'd that the game was too easy and boring. Okay, I will hand it to RS for the in-depth quests and storylines. But now with Cata out, WoW out-rivals RS once again for quests, lore and general leveling experience.
As for skilling, WoW has a far better system without a doubt. There are gathering and productive professions ("skills", for the rs kiddos) which make each player have their own way to make money or gear and spread these professions to the wider community for each realm. This, in comparison to the person fighting over the same tree or rock, makes for a more worthwhile skilling experience. Ultimately, the economy works a lot better than RS, especially without that GE and trade limit shit that ruined it so long ago.
Go ahead and throw some counter arguments at me, it will bring me some laughs. At the end of the day, WoW is by far the better game. Not to say Runescape doesn't provide some fun, at a reduced cost, but just isn't up to par with WoW. I've wasted far more years on RS and never got anywhere, but I've done that and more in WoW in less than a month. Just my experience I suppose, but I don't have the patience to stand in one square and click a tree over and over.
For most casual players, botting is simply out of the question for fear of being banned or for ruining the "experience". So don't give me any of that "ever heard of botting bro?" bullshit, because your argument is invalid.