Papa Meilland is a very good strong, deep red colour often with with a velvety lustre.
Oklahoma is a blacker red, darker and duller than Papa Meilland.
In my garden, Papa Meilland makes a taller, more robust plant than Oklahoma.
Both produce blooms that are exquisitely fragrant, though not particular long lasting either on the plant or in the vase.
Neither are particularly attractive, garden-worthy plants but Papa Meilland in particular is an indispensable bloom factory, producing its beautiful blooms on long, strong stems continuously throughout the year here in Perth, Western Australia. I have three plants and would hate to be without them because they are my first choice for a bunch of classic, fragrant, long-stemmed red Hybrid Tea roses. The plants are tall, angular, prickly and not particularly well clothed with leaves.
Oklahoma is, in my garden, less robust and the colour, while darker, is duller. The flower stalk is a little weaker so the bloom may nod slightly at times.
Papa Meilland produces classic HT blooms - high-centred with outer petals opening in a spiral. Medium to large with a good firm petal texture. It is at its most perfect as a partly open bloom. Oklahoma can be a little less formal in form, slightly globular and the petal texture is a little less firm than Papa M..
Both plants rarely set hips. If spent blooms are not removed, they eventually dry and drop but removing spent blooms encourages rebloom.
Papa Meilland is fine for the back row of the garden where other, leafier roses will screen its bare legs but it is probably best thought of as a rose grown for cut flowers rather than as a decorative garden specimen.