I haven't seen either live. Reports compare Stephensons stuff to Homer Bailey, for what that's worth. Maybe it's a good sign, or maybe that's just propaganda in case Bailey is a Ranger in 2015.
Tampa giving up Holmberg for an MLB catcher like Hanigan would suggest he has upside as a lefty starter, though probably a 4-man in a rotation. Hanigan, despite his bad offense, is considered a plus catcher and as a backup in Tampa, that's really a big deal.
The Reds have been on a mini-roll with farm pitching for a while. Not so much with balanced hitters and position players. They've had several kids drafted as middle infielders that "developed" as so-so corner infielders, outfielders, or defense only plate liabilities or utility at best guys. They drafted several power or whiff guys that are mostly still in double A or out of the organization. Catching is suddenly spotty in the organization.
Personally, I'd like to see the Reds invest a little more in better ametuer scouting and minor league development, and start answering more MLB roster questions thru the farm, than paying past prime players 10-20 times the MLB minimum to play bad LF and hit .240 for 4 out of 5 year periods of time.
Too many minor league players getting to MLB by hitting .250-.260 with K:BB splits that project into 150 K's, .300 ish OBP, and moderate power and speed metrics. On good teams, those guys become platoon and utility men for a few minutes. They sometimes get 2-3 years of full time chances with the Reds. The Reds farm is about middle of the road right now, but they probably don't have middle of the road money to make up for that at the MLB level without the farm. Fans always want to see spending at the big club, and they buy the tickets...but IMO, Reds need to look inside first.
I don't care much for farm system ratings. I would like to find a Bruce or a Votto every so often than a truckload of kids who are being fattened for sale to another club that just has to wait for that to happen.
In effect, getting Erwin or Winker or Travieso or Stephenson to the top level would be worth more than a pennant in the Southern League.
I just wish the constipation would end at Louisville. Send the players there and stock Bakersfield with Domincan League NDFAs.