I'm in the minority for hating the Moog LPF. The bypass was embarrassing. When people talk about poor, tone-sucking bypass this would be the poster child. Really bad enveloper. Combine that with the size and it was a huge turn off, regardless of the sound. You'll need an expression to sweep it manually. To get the most out of it you really need a robust CV controller which is expensive.
Rack filters are much more versatile, though you'll need some way to sweep them manually if that's your thing - MIDI foot controller or CV control which the Electrix filters still support. But really the rack products aren't that great either. The Filter Factory has no presets so you can't pre-program it. So unless you're using it with a sequencer or other controller that can send a TON of MIDI CC data you're left to fairly basic operations live. And you can't stack the envelope follower with the LFO, and the enveloper isn't that great either (two controls - whether it's on, and how much depth it effects), though it's much more usable than the Moog enveloper since it closes fairly quickly and responds pretty well to the actual attack. But for straight manual sweeps it's good, and you can get some good, basic LFO out of it, and it's SUPER easy to use. It's stereo, too, if that's your thing.
I currently have a MAM Warp 9 that has a TON more functionality, including presets, but it's a monster PITA to understand and program. Sounds great though, you get envelope ASDR with a ton of triggering options (1st trigger, 2nd, etc., trigger computed against LFO, all sorts of goodies), plus a ton of LFO options including stepped interval waves. Tons of good stuff if you 1) find one to buy and don't mind paying $350+ for one 2) can figure out how to program it 3) figure out how to bypass it since there's no remote/MIDI controllable bypass built in, so you need to buy another piece of gear just to turn it on/off in your signal chain.
With LPF filters there's a serious lack of really great solutions in pedal or rack form. They all have a lot of cons to go along with their pros.
I'm currently researching software filters in hopes of finding something that's even better than the Warp 9. Then I'll stick a laptop in my effects loop and control it with my MIDI foot controller. Great thing about software is there's a TON more options, there's current development where full featured rack filters seem like a dead product category (you're buying products from companies that don't even exist anymore), you can stack them, save presets, get a nice visual GUI to work with instead of whatever cryptic interface hardware provides. Guitar Rig 4 actually has some seemingly EXCELLENT modulation support with envelope ASDR, input envelope, 12-step sequencer, all of which can be applied to any control in any other piece of gear - amps, effects, filters, whatever. Apply it to a volume pedal, filter cutoff, multiple things simultaneously. Really genius stuff and super easy to use thanks to a straight forward GUI.
In case you can't tell I've been disappointed my my filtering adventure.
HUMBUG!
