Isomac is popular in Europe.  And like a lot of things that are popular in Europe, but that you don't see much of in the US, like public health care and free college, it's not because Americans are "smarter."  
 
The Venus was sort of a "deluxe" Rancilio Silvia, and in the early 2000s they were clearly aimed at the same market.  But in addition to having all the features of the Silvia, the Venus also had a slightly larger brass boiler, and added a brew pressure gauge. 
 
The Venus has the "chromey" thing going, and the cool Sputnik toggle switches, instead of the more "modern" Bauhaus look of the brushed stainless Silvia.   
 
But no one should assume that because Silvia survived, while Venus spun off into another galaxy, that the Silvia is "better." 
 
They are both "compromise," or "budget" prosumer espresso machines, for people who don't wanna throw tons of dollars at espresso equipment, or have the kitchen space (or spousal space) for a larger old commercial machine (the obvious preference around here!) 
 
Basically, if you're ok with the espresso that comes out of a Silvia, you should be ok with the shots pulled from a Venus.  
 
The biggest difference, is style.