It depends on the conditions, really. Gene by himself is good, but ultimately with James doing intel and Suzy and Aisha doing backup the man is god damn unstoppable. Spike, on the other hand, usually works with others as though each person is their own unit. So one on one Spike would probably be better, but with each crew together Gene would win. Then there's of course close quarters combat versus a shoot out. Gene may have more powerful weapons at his disposal, but Spike is the better marksman and more tactile. He fucking stormed a gangster hideout by himself! Even if Gene has his Light Shield, he still has to direct it or turn it on to deflect the bullets, and it also has a limited amount of use. You've got to figure that Spike has more ammo, so all in all I'd say in a shoot out it's Spike. If it were a fist fight, it would end up being pretty even, though Spike seems to have a better understanding of it. Now if they were to just to suddenl;y start a massive fight? Then I'd put my money on Gene in the end since he would probably be able to survive by himself until his crew came.
All in all, though? They'd go hit the town and go drinking all night, wasting money and bringing back cheap women.