Three factors i can think of currently.
Race
Force reserves
Preferred lightsaber style.
Let's start with the latter,
Obi Wan uses Soresu the lightsaber form of defense, where you hold out and wait for your opponent to lose energy, make careless mistakes and then strike.
Yoda however uses Ataru to combat his size disadvantage as it is the most acrobatic form which relies heavily on using the Force to move quickly, so due to this Yoda relies on the Force much more than Obi Wan.
I believe this is the order of this era of Jedi/Sith with Force reserves.
Yoda
Mace
Dooku
Palpatine/Sidious
Anakin
Obi Wan
-----Various other Jedi on/in the council/temple I don't feel like listing.-----
Lastly Race, Yoda has never revealed his species to anyone or where he originated, although in the databanks it's recoded as Lannik though this is not true, however it's possible they are genetically linked at some stage in Evolution.
Obi Wan is a human [No points for pointing out the obvious] therefore we all know his limits when not imbued with the Force.
A little information I thought i'd share.
Originally posted by sweersa
Of course, but next time pick a location that exists. 😛
So whats this? http://starwars.wikia.com/wiki/Apatros