No, there is no magic. The plus for a reaction is it is more subject to self-cleaning and less channeling at low flow rates. The plus for the canister, like a Ehiem ( 2011, 2015, 20 series. etc.) or Kordon Mod 4 ( no longer in production), is a higher BTFP ( Break Through Flow Point). So, better filtering at higher flow rates.
I'm an old Ehiem and Kordon fan and it would be my choice. Both of these have water entering at the bottom and exiting at the top. This is much better than others where the water enters and exits at the top which have lower BTFP and more channeling. You also need two reactors, one for GAC and one fir GFO. You only need one Ehiem.
BTFP = The flow rate where water begins to bypasses or goes around the media.
Examples:
A hang on the back box filter like the Fluval's that have partition plates. The BTFP is very low. Lets say 35 gals / hr. If you go above this in this design there is crap loads of bypass. So, you need to stay at that or near that BTFP of 35 gals /hr. A filter like a Eheim will be very high, say 100 gals/hr BTFP. However, on these Ehiem's, you can go 200 - 400 % it's BTFP and it will still be efficient due to its design.
