Apparently “Cardio after weight training is more beneficial for increasing muscle size and strength, but cardio before weights can help improve cardiovascular endurance.”
The general concensus from a quick go-ogle of various articles seems inconclusive – some say cardio then weights, others vice versa, spouting different pros/cons in each situation.
To get the best from both, a lot of advice is to do weights and cardio on separate days (or separate sessions on any given day – i.e. cardio in the morning, weights in the evening).