Which is better-2/28 ARM or 30 year fixed interest-only?

i am not clear with the types of mortgages that i am being offered. let me explain my situation. i received a commitment letter stating that i am approved for a mortgage (though i filed bankruptcy 3 years ago but my spouse who is co-borrower has excellent credit – about 720), 2/28 fixed/arm with 5 year interest-only period. the loan was expected to adjust after each half-year which i did not like as i had different financial goals. i was expecting to deal with the loan only for 5 years minimum as i would be paying off the car in 3 years and the bankruptcy would be erased from my credit report in 7 years. i am thinking of building my equity and refinancing in the 5 year itself with a lower rate. but i want to know more about the type of loan offered to me and if it can really help me build equity? what are the pros and cons? some other company offered me 30 year fixed with 5 year interest-only. pls explain this type of loan and can i refinance any interest only loan