The drawback of Reason is the internal engine which seems to EQ the end signal thatīs coming out of Reason (numerous tests can be found on the net on that issue), and the lack of VST support (hopefully supported in future versions?).
I've been using FLstudio for quite a while now and I must say, in combination with the right VSTiīs (Atmosphere, Reaktor, V-station, etc), itīs a killer application with an extremely good rendering engine (sinc 256 depth).
FLstudio is however a mediocre sequencer when one sticks with the supplied samples and synths, keep that in mind
And two keywords for FL: The pianoroll and automation
And as for the lack of MIDI sequencing possibilities in Reason.... FL supports (as does of course Cubase SX) Rewire. This makes it possible to plug Reason into FL (or Cubase) as a slave sequencer, thus giving you the best of both worlds: Reasonīs killer Maelstrom synth and the Subtractor, and FLīs sequencing possibilities.
Some tracks I made with FLstudio, using only VST's (percussion, pads, choirs, etc):