Glycemic index and blood sugar levels

I have been reading everything I can get my hands on about diabetes and glycemic indexes but have been unable to find an answer to my question so I thought I would post it here.

When managing your blood sugar what is more important, the blood sugar level attained or how quickly it rises. For example gievn the two following scenarios which one is worse:

Scenario 1 – food causes a rapid rise of blood sugar over a very short period of time but only attains a level of say about 121 mg/Dl (6.7 mmol/L)

Scenario 2 – a food causes a much slower rise of blood sugar over a longer period of time but attains a level of say 151 mg/Dl (8.4 mmol/L)

I am trying to get a complete understanding of my newly diagnosed condition so any insight is greatly appreciated.

Thanks in advance.

Rob L