Firebrand’s profiles are optional and not to everyone’s taste, it really depends what kind of image you’re looking for. If you want a very sharp image then the FBX profiles are the way to go, for a more CRT like image you should stick with the OSSCs generic modes.
OSSCs main advantages over those cheapy $20 converters is:-
Input lag – The cheap converters add variable lag between 1 and 3 frames, making it much harder to play your games.
Proper 240p handling – The cheap converters will add fringing/combing artifacts to moving sprites, destroy drop shadows and add other undesired effects, the OSSC does not do this.
Scanlines – OSSC can of course add cool looking scanlines.
Also you shouldn’t assume 5x will look best to you, experiment and see what gives you the look that you’re after.