Personalities:
1.  Ranma is hot headed, arrogant, impatient, and overestimates himself.
2.  Ryu has always been portrayed as the opposite of the above.

     Ryu can't adapt his techniques to the situation. They never change.
Ranma's techniques adapt to the situation.

Skills:
Ranma:
1.  Chestnut fist technique.  (I can't spell Japanese properly yet, no 
complaints. :-P)
 Ryu has assumingly faced off against Honda and Chun-Li in the past, so 
he's seen this before and would know how to deal with it.

     Ranma's chestnut technique is several times faster than Honda's or
Chun-Li's technique, not to mention stronger.

2.  Mouko Takabisha vs. Ha dou ken
 Ranma's attack is stronger but Ryu's will partially cancel it out.  
Ranma also telegraphs his attack, and Ryu is smart enough to notice.

     Ryu's Ha dou Ken is, in the Anime, a very slow technique to use.

3.  Hiryuu Shoten Ha vs Sho ryu ken
 Ranma's is obviously more flashy, but Ryu's is defintely stronger.  In a
manga published in the U.S. (Tokyama Comics I think?  Yes, I own it.) Ryu
commented that the odds on someone getting up from a *single* sho ryu ken
are next to nil.  Getting grazed by one is bad enough.  All Ranma's Hiryuu
Shoten Ha does (that I've seen) is toss someone high into the air. 

     Ranma is substantially sturdier than Ryu. Ranma, in female form, can
wield Ryouga's umbrella as a weapon. Furthermore, he can lift those chunks
of ice which Ryouga made out of the skating surface of the the ice arena.
As to standing up after a Sho Ryu Ken, I think he could do it fairly
easily. Ryu just isn't in the same class as Ranma. Even Ryouga isn't near
Ranma's level--once Ranma gets serious.

 Ryu is also in his 20s, 5 to 10 years older than Ranma.  He is 
definitely more experienced.  Any comments to this?

     But, he is slower, weaker, and his experience isn't as broad as
Ranma's. Seriously, Ranma deals with a much wider variety of attacks directed
at him.
     As to stronger, yes Ranma is. Ranma is shown to lift stuff which is
close to 15 tons in the manga. He is faster (with a mach 3 chestnut fist).
--
Ben Kosse bmk7411@cs.rit.edu
BGC Otaku and worshipper of the Red-Eyed Goddess. Member of ShAS.
Anime, RPG's, computers, poetry (read/write), music (listen/compose).
Author of the Bubblegum Crisis theme pack (see the homepage below).
Homepage with anime and other interests. (http://www.rit.edu/~bmk7411)