I own both these Power Supplies. Here are my thoughts after about a year of ownership...
The binding posts on my Siglent are 'weak' in that, for a lot of banana plugs, the slightest bump on the wire will make them fall out - and that's after I got new posts from Siglent and modified them (
I did a post on it here). I know the thread says 'solved' but I still have trouble with them. The binding posts on the Rigol are perfect.
The noisy fan on the Rigol annoyed me so I replaced it (
I did a post on it here). It's been near-silent and worked well ever since that modification.
The Rigol can be converted up to a DP832A with a 'magic' USB drive and a single command, the
thread on that is here. I checked calibration after converting mine to a DP832A and it was perfect.
I much prefer the UI of the Rigol, especially the 'pie chart' mode which has grown on me and the circular number pad is also very usable; on the Siglent all you can do is move the cursor to the number you want to change and turn the knob.
The Siglent has a problem that I have to crouch down to be at eye-level with the display to see the values that I'm changing but, if you used it in a setup where it was already at eye level, that would not be an issue. The Rigol display is clear from any angle.
On Channel 3, the Siglent can only do 2.5, 3.3, or 5 V and is 'limited' to 3.2A which makes it almost useless for powering small circuits that you want to limit current draw on. The Rigol has 5V, 3A on Channel 3 but it is fully adjustable in every respect. One downside of Ch 3 on the Rigol is that Ch2 and Ch3 share the same ground but the Siglent is fully independent (I think).
If I had to choose 1, it would be the Rigol, I feel it's bigger, better, beefier engineering and the UI is way better.