You pose a tough choice there

if you factor yr - miles - spec & performance in the 2 seater world the twin turbo E89 has them all beat but they do have flaws

you have had problems but i wouldn't say mechanical issues or reliability are concerns for the majority so perhaps you were unlucky or you didn't delve deep enough when you buying ( a glitzy main dealer can flatter the ego & loosen the wallet

)
Unless you crave a cutting edge in handling i would be tempted to try again only this time you should know what to look for .
They are great cars