vs a reg. How do you figure out when it's best to call here, or raise?

Which boards / under which circumstance would you be flatting a FD in a 3bet pot?

Hand History for Game 125014318389 (Poker Stars)
$50.00 USD NL Texas Hold'em - Thursday, November 13, 05:35:12 ET 2014
Table Anser III (Real Money)
Seat 2 is the button
Seat 1: k4ir0s ( $50.00 USD )
Seat 2: IamtheDerbst ( $50.00 USD )
Seat 3: FuchsJ ( $71.17 USD )
Seat 4: costelxx1 ( $25.33 USD )
Seat 5: djammusic ( $50.00 USD )
Seat 6: reckoner1986 ( $61.50 USD )
Seat 7: nickreason17 ( $65.18 USD )
Seat 8: payizan ( $59.66 USD )
Seat 9: zarplatka ( $50.00 USD )
FuchsJ posts small blind [$0.25 USD].
costelxx1 posts big blind [$0.50 USD].
* Dealing down cards *
Dealt to k4ir0s [ Kh 9h ]
djammusic folds
reckoner1986 folds
nickreason17 folds
payizan folds
zarplatka folds
k4ir0s raises [$1.25 USD]
IamtheDerbst folds
FuchsJ raises [$4.25 USD]
costelxx1 folds
k4ir0s calls [$3.25 USD]
* Dealing Flop * [ 5s, Jh, 8h ]
FuchsJ bets [$5.44 USD]