Really depends on what you like and how much space you have. I have two three sisters, one of which I use with a LRMSMSLR for stereo width before effects and the other I use in straight mono for color and (shocker!) filtering lol (or as an oscillator or in the fun formant zones…).
I like 3S cuz it’s the first analog filter (and oscillator) I ever used. It’s VERY quirky though. The inputs run hot. The resonance is extremely resonant. Most things you’d intuitively want to use the four outputs for (chords, comb filtering) you just can’t (hard to explain), but that forces more interesting uses anyway. I love it but man it demands some patience at first.
QPAS is very fun but never self-oscillates and it’s more challenging to mix stereo outs for width than it is to mid/side it for mono outs (phase cancellation).
Belgrad I’ve never used but Lightbath loves it. It’s big + mono so pair with a LRMSMSLR if stereo width is the goal.
Ripples + LRMSMSLR is what I’d say is prolly best. Simple, intuitive, sounds good. Weirdly, of the options I’m familiar with, Blades is really the only choice that feels ill-advised. Like the manufacturer has said directly ‘is not a stereo filter’
@varispeeder Mutable Instruments | Blades
Last bullet point under specifications. Sorry my initial post was unclear. To be more overt: my one claim here is “blades may not be the best choice for stereo width given its price, size, and strengths outside of that context, esp. if real estate is a concern.” I thought it might be useful to point out a cheaper and smaller option that could aid in your mission but if that’s not welcome then that’s totally groovy and if I’m demonstrably wrong about this that is also totally groovy.