If you've got the ability go for a Commission from the get go, then if you fall at any of the Officer Recruitment hurdles apply for Marine.
If you get in as an Officer you'll do all the same Commando stuff in Training as a OR Recruit, plus learn how to lead men (Under the 'guidance' of a senior NCO at first

.), plan and co-ordinate operations and eat meals with your elbows off the table.
As has been stated as you progress through the OR rank structure you'll get further away from the sticky end of the stick anyhow and with age and added responsibilities the attraction of lumping 100kg of kit around in the field and then 'Winning the firefight' will probably wane a tad.
Good luck with your decision and future.