I posed the same question must have been months ago, except that I wondered what the outcome would be if '03 Spurs played the '05 Spurs.
Robinson/Duncan tandem -vs- Duncan/Mohmd/Rasho/Horry,
Kerr/SJax -vs- Ginobili/Berry/Horry
Parker -vs- Parker/Longoria
Bruce against himself
I would put '05 over '03, simply because of the familiarity level of knowing the "system," more smarts.
But '03 certainly would have it over '05 in the 2nd and 3rd quarters because they had more energy and were less predictable.