Several of the new QD mounts on suppressors nowadays are very repeatable, such as the Silencerco Omega and their mounts (which also work on a couple other Silencerco models) and Surefire SOCOM series mounts.
I know that with the Silencerco Omega, the Q portion of QD is pretty relative. There is enough threading and locking that the only thing quick about it is that it is easier to start the threading process than with a direct thread.
Find a suppressor with a good QD mount system, and your results will be repeatable. The downsides to them as noted is that they may be a bit larger and a bit heavier because you need the mounting gear on both the suppressor and rifle. Also, there are more mechanism to break.
Direct thread is certainly repeatable. They can have a tendency to walk off the gun if you are not mindful and are a high round shooter.
The downsides to direct thread that I had seen is that accuracy may fall off if the suppressor does come loose and that damaging the threads on the barrel can be very detrimental to easy of mounting. It can be harder to get the threading started and more time may be involved in spinning the suppressor on the barrel.
Personally, the time issue is NOT a factor in anything I do.
Mobuck mentioned POA/POI shifts between unsuppressed and suppressed guns. Despite the claims made by some manufacturers, using a suppressor will not necessarily tighten up your groups. It may open up your groups. Also, it may throw your groups off by very little to 5-6". I have tested this on several guns on my range, talked to several suppressor owners and gotten their feedback, and watched a lot of the videos on Youtube that have shown some minor testing of this at distance (usually 50 or 100 yards - I test at 100). Some manufacturers will (or have) claimed "little or not POI shift" with the use of their suppressors. This is no more valid than the claim of tightening up groups.
As near as I can tell, putting a suppressor on a gun most definitely can affect the POI. It seems to have a greater impact on thin, light barrels than big, heavy, bull barrels, but this is not 100%. Putting the same suppressor on two different guns can result in dissimilar POI changes, but putting the same suppressor on the same gun should result in the same changes (with the same ammo) every time. Trying different suppressors on the same gun may get different results as well. Let's face it, when you put an extra pound or so of weight on the end of your barrel, it is going to affect the barrel harmonics and potentially droop...just like resting your rifle barrel on something and shooting may affect the POI.
So a threaded suppressor may not have a POI shift in the sense of repeatability, but it certainly may have a POI shift between unsuppressed and suppressed.
I don't know what is available oversees, but one of the reasons I went with the Silencerco Omega was because It can with parts to make it a direct thread suppressor or a QD suppressor. So I am good either way.