BD190, ask yourself why did you even applied for the 767 job in the first place?
You're probably like me, fed up with 4 sector, min rest, max duty days, and want to expand your horizon.
I don't know why everybody is so hung up about 4 stripes. I agree with Dani and Pete77: it's all about lifestyle. You only live once, so you might as well enjoy it!
I left a regional low cost jet company (with outlook on a command) but where I was absolutely miserable, to fly long haul cargo and my life has improved by 100%!
Regarding job security: who knows... Waiting a year for a command (especially in today's uncertain economic times!) is a mighty long time! Building on that command and having a sensible amount of experience will take another year. In aviation two years are an eternity!
Regarding the "once a captain, always a captain" statement, that all depends IMHO. Sure, you can keep your command and become a direct entry captain for some regional or low cost company, but remember that most companies that take on DEC's are usually not the best companies where you want to stay until retirement. As a captain you'll be stuck in regional or low cost companies for your entire career, unless the E190 company you work for now expands into the long haul/wide body market and you have the appropriate seniority to stay in the LHS. I met plenty of burned out captains in their 40's and 50's in my last outfit who were stuck in the LHS because they did not want to take a pay cut and move to a RHS for a decent outfit.
"Captain on the E190 will lead to captain........who knows!" From captain E190 to captain on, say. captain on a wide body? Hahaha, forget it! You will have to join the seniority list of that wide body outfit as an FO, just like everybody else, so if that's your goal you might as well make that move as quickly as possible.
Remember, these quickie command companies usually have a major price tag attached: lack of lifestyle and lack of human terms and conditions!
Carpe diem!