I think of them as completely different in function. One is a standalone, the other is a filter with an effect loop, allowing the filter to apply to everything while still following the original signal strength.
If you're really invested in having more control over your sound, the Wonderlove makes sense.
If you don't really care about having that additional control, then the Riddle is overkill. You might as well get a Mooer Sweeper at the low end, or a Source Audio Manta or Stingray for something more versatile.
I'm not saying it's bad to want either more or less variety. I've owned quite a few envelope filters from 3leaf, starting with the Groove Regulator, and have owned various EHX filters as well. (My Qtron+ was replaced by the Groove Regulator because the GR didn't need a compressor to prevent spikes in the audio from the resonances.) I've even owned the lowly Mooer Sweeper for a tiny board.
With all that said: OP, what are you imagining when you are thinking about using such an effect? How do you want to use it? How much and what kind of sound variation do you want (both filter and dirt)?
I've bought my first envelope filter not too long ago, so I'm still exploring how I want to use it exactly. I started with a Q Tron, and now I have The Riddle. I love the blend control, so I was googling other EF's with blend, and the Wonderlove looked interesting. I was wondering if the price difference between the two is justified. Controls are more or less similar (wouldn't need a boost knob. do you find the tone knob useful?). So it comes down to if I would use the effect loop (no idea... would probably have to play it for a while to find it useful or not), and SOUND QUALITY...
Regarding the effect loop, it's about whether or not you need, or even just want, more than one kind of dirt in the effect loop. The Riddle has one kind of dirt in that position built in. The Manta and Stingray have multiple kinds of distortion and fuzz built into that position. The Wonderlove lets you put a pedal , or chain of pedals, into that position, or even to do side chain triggering, like following the mic'ed signal of the bass drum so the filter is open corresponding to the drum hits.
I use the FX snd/rtn on the 3 leaf Wonderlove for Octave pedal(s)
OC-3 or been dying to get a Salvation Mod Vivider and place in the FX loop of the Wonderlove.
the clean signal allows the octave to track better.
I finally played the Wonderlove this week and it's fantastic. One thing I notice about it and the Proton is a kind of high fidelity, very natural quality to the effect. No glitchy triggering, very smooth.
When it comes to an envelope the test (for me) is how good it sounds with the envelope going down instead of up. I couldn't dial it in on the Proton, the Wonderlove was very easy to dial in. I would equate the EHX Qtron+ to the Wonderlove over the Riddle. Both are more Mutron-like.