I myself prefer finger locks before wrist locks, and in actuality for me it is easier to apply an arm bar on a person than a wrist lock. HOwever, having said that, an arm bar as jkogas said is easier because it's considered a big joint/target. In MMA they do not allow the small open hand strike to vital targets that would cause distractions and permit easy access to wrist and finger locks. No attacks to the throat, eye gauges, groin shots, pinching ect. The stuff that I consider real and simple self defense.
For me once I have finger or wrist lock it is very easy for me to transition into an arm bar or shoulder lock and tons of other locks and holds.
"Poor is the pupil who
does not surpass his
master" - Leonardo Da