Mate of mine reckons for the next two years we have big chances of winning the Youth Cup, there's a lot of talent in the next two years of academy scholars.
As for those listed above, I expected to see more of Garbutt next season, as I get the feeling Martinez sees something in him and will give him more chances this season (referencing him in interviews a few time etc), whether he'll take them I'm not sure. Browning is the other I'd expect to see a lot more of in pre-season and maybe some of the early cup and Europa League games, as he had a pretty consistent presence on the bench by the end of the season. The injury to McAleney last season I think has really set him back, I'd expect him to go out on loan next season.
As for Ledson and Kenny, I think they'll spend most of next season in the U21s and shining for Everton in the Youth Cup, maybe a few cameo appearances for Ledson if he's really pushing on.
For the poll above though I went for Kenny, assuming Martinez is here for at least another 4-5 years, I think he has all the qualities Martinez looks for in a defender and his limitations aren't as big an issue for Bobby and the way he plays.