5 months ago I was in a similar situation and came to pprune for advice. I was given the oportunity to upgrade on the CRJ and also to go elsewhere as a 757 FO. In my case the CRJ upgrade and 757 new hire class where within 2 days of eachother. The CRJ paid WAY better than the 757 as well. I chose the upgrade and was advised by all to do so. Im glad I did! Im building valuable PIC time and have a very nice paycheck with a bright future.
In your case you say that you might upgrade in a year on the E190, but the 767 FO pay is better than the E190 CA pay. This is a much tougher decison... In aviaton you can not guarantee whats going to happen next year meaning that upgrade may not happen... Also the 767 money sounds tempting... Do your homework on each company and figure out what your ultimate lifestyle and career goals are.
Sorry I cannot offer better advice, but if the upgrade was guaranteed now, I'd do the E190 gig (provided it fit into your lifes master plan)!