Owned the K5 in the past, currently, using the K30.
In terms of buffer capacity, I can't comment much. I seldom use at this mode. I felt both are about the same.
AF accuracy, it seems quite similar in good light condition. But when it come to low light or bad lighting condition, the K30 did well. K5 does not give me confidence that I could rely on its auto focus.. Normally, I like to shoot the concert at Esplanade, using the FA77 or FA85, with K5, I need to manual focus during the concert, K30, I tends to rely on the AF. I do not have any DA* lens, so can't comment on it.
I will say go for the K30 for the value of money, live view advantages over K5 also...
Only I felt is the battery life, K5 is still the best.