Except for lounge access in the US, American programs (all) are a lot more generous than Eurobonus. I will talk about United because it's what I know, but this is just to give you an idea:

* 100% miles earning on all fare classes including deep discount economy. This applies to UA and US metal, other * airlines are case by case but in general earnings are more generous than if accruing to EB.
* 25% mileage bonus for 2P (* silver, 25K miles to qualify), 100% for 1P (* gold, 50K miles to qualify) valid on UA, US and LH transatlantic.
* Many many promotions to pile up lots of miles (credit cards, double mileage promos, ameniti, etc).
* Domestic upgrades are not free on United but you get 4 500 mile upgrade certificates for every 10K miles you fly on United metal. If you don't use them they turn to miles at expiration.
* Lower redemption levels, even after the October 2006 increase.
* In general, you also get more recognition if you fly the airline you have status on.


United has a weak presence in EWR so I'm not saying it's the right program for you. I just wanted to highlight some of the huge differences between Eurobonus and a typical US program. For me, these differences far outweight lounge access.