i have had both, a disc swap and a modded PS2. i had problems with my disc swap, it does not want to play all game, what it does is allow you to bypass the first (but only the first) security code upon loading so your system can reconize a foreign game which are usually blocked from being played on your system, however some require multiple loading throughout the game many games upon the second load will freeze up. it also did not want to play PS1 games as well, . i do not know if the newer system will have this problem as well. i would recomend waiting for a mod to be relased or if you cannot wait just get one of the newest systems (before the slim) released with a mod. thats what i have and have had no problems what so ever .
chris