Have both the Gaomon S620 and Wacom CTL-472.
By no means am I an experienced player having tried and tested all of them out there, but I have done a fair amount of research.
Got the CTL-472 tablet 3 days ago, and I must say that although the S620 is a great tablet, one of the favoured ones, the CTL-472 is simply a refreshing experience for me. As mentioned above, smoothing is a big thing that you will notice when using a tablet, especially once you get to faster maps with jumps. With the CTL-472 I do not feel said smoothing, whilst with the S620 there is slight smoothing (Open TabletDriver helps with reducing it)
I also believe the CTL-472 to be on par with the CTH/CTL-480? (King/Queen of Tablets for Osu?, other, more competent people may wish to validate my statement and confirm for you.
I am aware that differences between the two do exist, such as the pen and also overall size of the tablet itself.
The CTL-472 is widely available, and much easier to get a hold of, in contrast to the CTH/CTL-480.
The build quality of the CTL-472 also feels more robust, and polished, when compared to the S620's.
One thing I noticed when using the CTL-472 is that the cursor tends to chatter (cursor being shaky when standing still) and is not as stable as the S620's but it is minor and for playing Osu I do not see as an issue. You can also get rid of that using the Open TableDriver and applying the Devocub Antichatter filter. A little bit of it is acceptable, as it is normal due to the tablet's sensor. It is actually considered a good thing, as it acts as proof that there is no built-in smoothing. It also shows just how direct your input from the tablet is, with no effects and smoothing trying to cover it up and eventually impede your gameplay.
The S620's surface is smoother, so gliding across it is easier, preferred by players who drag their pens.
The CTL-472's is grippier? (feels a bit like gliding your pen on rubber, but not, as it is still smooth ... hard to explain. Hence, you will be running out of pen-nibs quickly if you were to drag. I would suggest getting a cover for the tablet in that case to eliminate the problem. If you hover, then it would pose no concerns.
Answer might be irrelevant at this point, and a bit too long. Apologies for that.
Thought it would be best to share as much as possible, and assist with your decision.
Any additions/corrections to the stated above are welcome.