Regular flash will net you sharp color pics at night, but will spook animals more than the glow of the IR illuminators. Animals don't notice the IR illuminators unless they look at the camera, which they may do because the camera will make a noise (most brands) when it takes a picture. With the Moultries, it is when it moves a lens (I think). With regular flash, animals not looking at the camera will still notice the flash and potentially be scared off by it.
Asking what is best is really vague and won't yield you meaningful results. There is a LOT of variation and a huge price range. With the Moultries, you get an intermediate lag/reaction time between sensing movement and taking the picture. I believe it is 2.3 or 2.5 seconds (at least on the IR models). On the Stealthcam like Sportsmansguide has for about $100, the lag/reaction time is slow and is closer to 5 seconds. It is good for things like watching feeders, not watching trails.
Illumination is an issue. My Stealthcam has a round illumination that does NOT occupy the whole image. That is a bad thing. It has good range/throw, but not much scope. The Moultries have slightly less range, but much better illumination across the entire image.
Then you can consider things like multiple images. Several claim to have burst modes. The Moultrie burst mode will do up to 3 images, but they are about 13 seconds apart. The Stealth will do up to 9 and they are about a quarter second apart - huge difference.
Then there is image quality. Honestly, I don't think that 5 or 6 megapixels is significantly better than 4 for game images. You can spend an extra $100 and get the I60 by Moultie and get two more megapixels, but I don't think the difference is worth it (compared to the 4 megapixel I40). The Stealthcam is 5 megapixels and takes great daylight shots, better, I think, than either Moultrie, but the night shots are poor because of the poor illumination.
The I60 also has a tiny view screen. It is not very useful. Don't buy the camera for the view screen.
I find the Moultries easier to use than the Stealthcam. So that is another issue to consider, ease of use.
I find the Moultries mounting hardware to be more user friendly than the Stealthcam as well. So ease of mounting...another issue.
Then there is battery life. The Moultries use D batterys (6) and the Stealth uses C batteries (9, I think). The D batteries seem to last longer and so are a bit more cost effective.
Those are the two brands I know about. I have 4 I40s, 1 I60, and one Stealthcam. There are other brands. Some may have a better reaction time, but most all will claim to be quick. I think the fastest was a half second. I found once (and don't recall where) a site that reviewed a half dozen models and tested reaction time, flash distance and spread, and gave some general descriptions. For general purposes, the Moultrie is pretty good without spending a lot.
Interesting thing about reaction times on the cameras. If too fast, the animals you with to photo may not have time to move fully into the image. If too slow, the animals may pass all the way through before the camera takes the image. With the Stealthcam, I can't use it for a trail cam and expect it to do a good job because of the lag. The Moultrie does pretty well, but you don't want it shooting across a trail, but down the trail.
One thing to look at is the number of IR LEDs. Several cameras have only a few LEDs like the Stealthcam. This tends to have a negative impact on the camera's ability at night. More is better as a general rule.