it depends on what type of modding i would recommend you to start on xbox as i have been modding for last 3-4 years and would gladly help you out if you were stuck but you need to be cautious when you first start out as you dont really think that much about consequences just getting down to it, but if your starting of and have never modded before try iso modding games like gta 4 or waw zombies i have both of them and will walk you through the steps if you want then when you get better i will help you iso mod new games like gta 5 and if you want etc.........so just pm me your gamertag on ttg if your on xbox and you want help ill help you (IT DOES NOT MATTER IF ANYONE WANTS HELP ILL TRY TO HELP AS BEST I CAN)

Ps3 is much easier from seeing them mod

Ps3 is safer to mod on they do ban but no where near as fast Xbox.
Tools Ps3 a cfw or Jailbreak.
Xbox getting a flashed drive doing simple Iso mods and you can get free games as well.