Here is the good and bad with lighting.
Actinics - Good because they only put out the light spectrum corals need for photosynthesis. Bad because since the bulb is only putting out one small range of wavelength the PAR numbers coming off of them are much lower than daylight. Also bad because other wavelengths do play minor, yet important roles in the coloration of corals and actinics by themselves won't give you the best coloring to your eyes or in reality in the corals.
Daylight - Good to make your tank look more like day time lighting. Also good because most daylight bulbs put out just as much PAR in the 440nm range as an actinic so they are about even as far as lighting for corals are concerned. Another possitive is the other spectrums do bring out certain pigmentation of your corals to make them look better. The Bad with daylight is the same though... since they do put out a broad spectrum, the other 2 "peaks" in wavelength intensity is in the bad areas that promote algae growth. They have to put those in daylights though to balance out the blue spectrum and make it look more pleasing to the eye.
This is why I am now learning just recently that PAR readings by themselves are almost meaningless, just like wattage. PAR is from 400-700nm in wavelength, which is most of our visual range as well. 400 being deep blue until it drops off into the UV spectrum, 550 area is Green, 700 is Red, beyond 700 is Infrared. With a reef tank, your primary concern is coral health and making sure they get the lighting requirements they need. For corals, this is mostly 440nm area.. actinic. With a PAR meter/reading it will give you the total PAR output of the light, so it takes into account 400-700nm and gives you a number. Problem with that is, we are really only concerned about just the 440nm area, the others play just minor roles in corals. So what I am saying is, an actinic bulb will only give you a 300 and below PAR reading where as a daylight bulb will give you a 1000 PAR reading because it has more wavelengths of light to figure into the equation. Unfortunately, with just a PAR meter, you do not know how much of that 1000 PAR on the daylight bulb is actually just 440nm and how much is "bad" light for the tank. This is where a spectrometer comes in handy, you can break down the wavelengths of the daylight bulbs to see how much of each wavelength they put out. On my Phoenix 14k MH bulb, under a spectrometer, it appears about 75-80% of the output of the bulb is in the 440nm area, which IMO is VERY good for a "daylight" bulb. On the other hand, the bulb I thought was the best of the best at the time, the XM 10K, put out about double the PAR as the 14k bulb, so by a meter reading alone it does appear to be 2x as good of a bulb as the other... but then you put it under a spectrometer and realize that only 30% of the light coming out of the bulb is in the 440nm area, making it actually a worse choice in lighting if your looking for coral growth. I just recently learned this information on my own by buying the equipment to do so. I had always had questions on lighting.. and I knew there was more information than just what is commonly out there, so I had to figure it out on my own. I have learned that even 1 year ago what I thought was the best lighting out there for my tank is actually not good at all... it works.. but I could accomplish much more for less $. I am correcting my mistakes now.. but this hobby always has something to teach you.
Edit: Ooops, all this talk about lighting, I meant to give my opinion on the original question about flow. IMO I think 20x turnover is bare minimum for a saltwater tank. Just my opinion.
