Good morning Jean-Marc
My advice if you've narrowed your decision down between an Excalibur and a Hegner would be to try both machines out at a retail outlet that have them on display. You'll then nail your final decision down to one or the other either because of features, ease of use, size, looks may be a factor, service after purchase, budget in mind, longevity and etc. Both are high end and fairly high priced machines. Also search reviews on each but take them with a grain of salt.
Like Hans mentioned size of crosses you plan on cutting can be done on any scroll saw.
I have an Ex 30 that I've been using for the past 15 years. The reasons I chose it was size, quality (domestic made), ease of use, and service after purchase. I've never had to look back on decision made then. Good luck with your decision.