It's true that the Strada EP can't reduce the flow rate below line pressure, nominally 3 BAR. That's too fast for long PI shots. The EP is a pressure profiling machine, not a flow profiling machine. It does pressure profiling by varying the speed of the gear pump. But in my experience pressure profiling has limited benefit, especially with light roasts. It does allow you to grind a bit finer and get somewhat slower PI, and also lets you slow the ramp to full pressure, which helps if your distribution isn't perfect. Perhaps the biggest benefit for light roasts is the ability to reduce pressure after the peak to keep the flow rate constant. But this won't work anywhere near as well as ultra-fine grinding with long, slow PI, ala Slayer.
So I agree that if it has to be an LM, then an MP with the conical valve is the way to go. While it's true that it may be harder to reproduce shots with the MP vs, say, the Decent, from what MP owners have posted here it's possible to do so with practice. The water waste is regrettable, but not if you're just making a few drinks per day.
Personally, I'm a fan of manual control versus automated "profile following". I've modified my GS/3 AV with a gear pump, a needle valve and a bypass solenoid. This allows me to do both flow profiling and pressure profiling, the best of both worlds in my opinion (the old Slayer couldn't do pressure profiling because it didn't give you dynamic control of the gear pump speed; the new Slayer has a rotary pump with constant speed -- i.e., pressure profiling is physically impossible.)
I like to watch what's happening and adjust the shot parameters on the fly, as you might with a lever machine. While I can do a somewhat automated shot (fixed PI time followed by constant pressure until the target beverage weight is reached), I prefer to switch from the PI flow rate to full flow rate when I see that pressure has stabilized at the peak, and when the flow rate begins to increase I manually reduce the gear pump speed to keep the flow rate constant (my setup monitors the GS/3 AV flow meter so I can follow a numeric representation rather than eyeballing the stream.)
With a bit more coding work I could have implemented fully automated shots like the Decent does (and as our member AssafL has done with his modified GS/3 AV), but I think there's enough natural variation from puck to puck to justify keeping my hand on the tiller, so to speak, and I'm only making a few drinks per day, so automated flow/pressure profiling isn't necessary like it might be in a cafe setting.
I have similar feelings about roasting. My setup is capable of using Artisan's profiling following features, but I prefer to adjust things on the fly based on sight, smell, sound and data coming from Artisan. If I roasted commercially, I'd likely use automated profile following, but it's not necessary or desirable for home roasting with a small machine.
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