As the topic suggest, it may be apparent that my question is relating to the current HX offering from Rocket. I am in the position to transit from my existing full-automatic to semi-auto, therefore I have no real experience with semi-auto but I have learned some theory and technique from this forum and the internet.

My question is not limited to particular brand, but when there are two HX machines, one equipped with PID and one with rotary pump (which I learnt to have slight edge over vibration pump), how much difference are there in practice and does it justify the price difference?

I understand that PID on HX machines "is useless" due to the heat loss from exchange tube to group head so it would not work same as installed on single / double boiler machines and all that, which I read from other post in this forum. However I quite like the idea that PID could maintain a rather constant temperature control of the boiler, which helps with consistency when trying out and producing repeatable results. (*please comment if my concept is correct) I understand that although the PID will display a higher temp than the actual brewing temp, it has a higher sensitivity to respond to temperature drop compare to the use of pressures stat. That's all in theory that I learned, but how it performs in real world situations? If what I described is correct, why does the Rocket Evoluzione V2 remained with pressure stat?

Now without PID, the Evoluzione V2 has the rotary pump and capability to switch between reservoir and direct water supply, I understand these features are slightly more advance than vibration pump with reservoir only. I also heard that rotary pump produce a nicer profile of water recovery which tends to benefit the consistency of brew temperature throughout brewing process. (*again please comment if I am correct about this) I mean the temperature drop would not be so much with a rotary pump from the begin of pull till you stop the brew. Is this noticeable in real world situations?

Obviously I see the option to switch to direct water supply is handy for future proof purpose if not being used straightaway, but all comes down to the question: Is it worth to pay the extra for rotary pump and direct water supply? or having a PID to have more control on boiler temperature for shot consistency is more important? How useful are these features in real life and what are the priorities if to put in order?


Thanks

Like you said yourself a PID on an HX is "useless". The temperature consistency is controlled by the cooling flush. A pressurestat will do the same job as well as a PID on an HX.

A direct water conncetion is a great option if you can make use of it, otherwise it is obviously useless. But you can use a Rocket machine, or any similar machine, for more than a decade, so you may find it useful later in your life.

Rotary pump vs vibratory pump apparently makes no significant change in taste, but a rotary pump is a lot quieter and it has a longer lifespan. A rotary pump is a commercial heavy duty option meaning many things. To me, mainly that there's no worry about duty cycles when backflushing with detergent. And now that I've gotten used to a machine with a rotary pump, I couldn't go back to a noisy machine with a vibratory one.

As for whether these options are worth the extra price - that is for you to decide.
A machine with a vibratory pump is quite capable of producing great espresso. You pay more for the convenience.

Neither will make any difference in the cup whatsoever. PID and PSTAT will effectively do the same thing. Rotary will be quieter and last longer, but is more expensive to replace. Vibration pump is noisey and won't last as long but is cheap to replace (about $50).

But price being equal , I would take the Evo will rotary pump and ability to plumb in over the v3 PID plus.

Get the rotary.

Plumb vs. reservoir? PLUMB!
Plumb with rotary pump... priceless!

With a Quick Mill Vetrano 2B with a rotary pump, you do <not> need to plumb. It is, however, an option if your set up changes. I went for the 2B because its PID is not about the boiler temp, but the actual temp at the group head.