Are you able to keep an eye on them? Down here in Texas I have to travel 4 hours one way to my lease so I have to have a dependable feeder. There's nothing worse than one that does not work everytime.
#1 remember, Good stuff ain't cheap and cheap stuff ain't good.
Solar powered is a positive.
Electronic timers are a plus.
get one that you can set the rate and times of feeding.
If you build your own as Aussie guy did be sure that you can get replacement parts at a moments notice.