Both are fine spots--I suppose it comes down to whether or not you prefer a buffet, or a bit more costly table service spot. WE always dine at Jiko's these days, and will do so again in May. While that tenderloin is supurb, I've been converted to the Berbere Braised Lamb Shank--mouthwatering-ly good!!
As noted you can't see any of the animals from the restaurants. If you do wander around the Lodge and go to the animal "viewing areas", a lot depends on what time of day it is. We eat at Jiko's around 6:00 and usually stroll out to look at the Animals just prior to dinner. In 5 trips, all we've ever seen are a few lazy, sleepy cattle and some birds. I thought I saw a Zebra in the distance, but Mrs. Uncleromulus says it was a mirage. In a word, you won't confuse this with the safari ride over at the AK Park.