Quick Question: Reigate to Rugby tomorrow morning - M1 or M40?

[Big News]

Just a quick one - I've got to get to Rugby for a wedding tomorrow morning from Reigate (J8 M25); do I take the M1 or M40? I'm not a commuter so I have no idea of the benefits or drawbacks of each between 08:00 and 10:00...

Thanks in advance!

[dfen5]

M40. Get off at Banbury, left towards Banbury, straight over a couple of roundabouts and then right onto A423 to Southam and then A426 to Rugby.