I'm looking at some strobes to fill 48" octaboxes or 60" x 90" softboxes. I'm looking at the SK300II or MS300 but I can't figure out what the heck the difference between these are aside from a small difference in recycling time.
Also, is 300 watts enough to fill these softboxes adequately?
Personally power has nothing to do with if the strobe will fill a modifier of a given size. How much f-stop you can get at a given distance from the modifier is a different thing. Having used flash tubes which are open, I prefer the newer design of Godox where the tube is covered in glass but those are more expensive.
You haven't said what you plan to photograph or how large an area that you will need to light, what color the walls and ceiling are, distance from light to subject, etc. It all enters into "how much" light you will need formula. Trying to shoot a totally black subject in a totally black room is going to take a lot of light, so by comparison to this and with nothing to go on, I will tell you what I have.
I have both the MS300 and the SK300 in use in my small home studio. I primarily do portrait and product photography in my 18 X 26' shooting space with a 7' 11" ceiling. The walls and ceiling of the studio are all painted "Ceiling White", so I frequently make heavy use of them as " white reflectors". I have found the 300 watt second mono lights to be plenty of light for the work and space that I'm in (wish it was 10' high). In most cases, I'm running them at less than 1/2 power into 32" or smaller soft boxes or umbrellas, but I do occasionally use a pair of 14" X 60". When larger and softer than these is needed, I usually resort to reflecting off the ceiling or walls, sometimes with an added diffuser, and in this space I still haven't found that I needed bigger lights.
I think that I like the build quality and appearance of the SK series lights a bit more than the MS series, and I like the fact that both have the X series of radio receivers built into them. The SK 300 are slightly longer in size than the MS300, and in my opinion, have a bit "more sturdy" feel to them, but they both do a great job and seem to be solidly built enough to survive years of use, but then I haven't owned them long enough for a very good evaluation either. Both models have been very reliable over the past year and a half or so that I've owned them.
I also have a Godox DP1000 III that I bought to power a focused lens for projecting patterns and colors on my backgrounds. Having tried to use one of the MS300 lights with this lens, I quickly decided that I needed a "bigger light", but I wanted to stay with a mono light flash, as opposed to a continuous light source. I had no idea how much bigger would be necessary, so I bought the DP1000 III (I think I way over bought this time). An SK600 would likely have been sufficient for this use, as I think the DP1000 is almost bright enough to vaporize the backdrop at it's full power. I doubt that I'll ever try full power again.
If I can help further in your decision, please reply with some information about your shooting space and what you will be photographing. The more that you can provide, the better our answers can be.
I thought the MS200/300's looked interesting, especially for the price so I was able to borrow a couple to use at my studio lighting workshop last year. I wanted some extra lights to supplement my four AD600's I was using plus I wanted people to see an inexpensive option. I expected these lights to be pretty inconsistent in power output when set to low power settings. That's usually a sign of a cheap light. I was very impressed that they stayed within 10% at all power levels and multiple test firings. For around $100.00 USD that super impressive.
Now the build/durability may be on the light side but if I wanted to have a set of "plug-in only" lights to carry to venues and such, these would be my pick for lightness and accuracy. Plus they are so cheap I can have plenty of spares for when I break them.
The SK series are a bit more durable and likely recycle faster but they are heavier and larger.
