What are you looking for the machine to do?  A shop machine?  Home machine? Catering?  A dual boiler machine typically has a much quicker recovery and also allows for better temperature stability in the brew cycle.  

 

 

Its a good question with many answers. There is a ton of info out there discussing the differences between double boiler and heat exchange machines.

 

From a usability standpoint, it comes down to control. You can achieve great temperature stability and control with the current crop of top-of-the-line machines of both types. You may get better temperature control with double boiler machines at the upper-mid-range price point, however there are several upper-mid-priced hx machines that will deliver great espresso in capable hands.

 

That last statement is really the most important part, by the way... "in capable hands".  I tend to think that if the hands are capable, the differences between good machines of both styles are not as big of a deal... and if the hands aren't capable, you have bigger problems to deal with.

 

Yes, the differences apply to machines of all sizes.

Go for a double boiler. You will have more stable heat in your shots, which is crucial. The cost will be worth it, if you are intending to create great espresso.