If Tramadol 100mg equates to 10mg of morphine, and oramorph 5ml the same. How come oramorph is considered stronger?

Concentration. I think you need to be careful with the concentration of the oramorph, since 5ml does not give any indication of the amount. If it is 10mg/5ml, then certainly that is equivalent to 10mg of morphine, and roughly equal to 100mg of Tramadol. Keep in mind, however, that different people get different results from any medication. There is no absolute "strength" when it comes to pain control.
Equivalence. They may be considered to have an equal effect in trals of pain patients but morphine like products are in a different schedule,have more side effects and have more addictive properties and in my personal opinion are more effective.