If you are drooling over the ECM Giotto then get the gorse out of your pocket and buy it!
I dont know the Isomac Relax but the Giotto is much tested and I would go every time with a known quantity ie. a machine that is perhaps overhyped and somewhat overpriced but one that will deliver the goods and wont disappoint. It should also have excellent resale. If you try to sell an oddball machine one day that no one has heard of, you will be in trouble.
Just my general opinion. Mind you I like commercial machines with rotary pumps or dual boiler machines. My preference.
If you want to go for a nice shiny E61 hx machine then the Giotto is probably the one to go for.