After a PhD in biotechnology/engineering - more opportunities in industry or a postdoc positions?
I don't know much about bioengineering and materials sciences. In my area (CS) there are many more industrial positions available than academic positions. 

However, industrial positions often tend be clustered in regions, and there might not be too many academic jobs in those regions (or they might be very highly competitive). 

Sadly though, I suspect that basing your decisions on where you might do a postdoc is a problem, because a postdoc itself is a temporary position, and so you're really only deferring the real problem. One argument would be that if postdocs in your area take a while (say 3-4 years vs 1-2), then you might as well operate as if that were the permanent job, and then reevaluate after your time is done and you're on the academic job market. 

Good luck: two-body problems are tricky, and when one partner is on the academic track it gets even trickier.