Both in-ears are come from rappers and both advertise their in-ears as a pair of in-ears for HipHop genre but which one is the best choice for you ? Many may say Beats is about fashion and it comes with not so good audio quality, but in my opinion, I think it is about a sound character, I think Beats Tour is a dark tone in-ear,
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with this sound style in-ears, you may not get a hi-tone with crisp as a bright tone in-ear like SOUL by Ludacris SL99, In contrast I believe many people labeled SOUL Ludacris SL99 as too bright in-ears or it comes with unbearable hi-tone. So, it is not about which one is better than other one, but it is about what type of audio character that you like.
But it is only about that, price is also other factor to defines which one to buy with the price of Beats Tour, you can buy a mid price audiophile headphones like AKG K240MKII or Marshall Major FX, but SOUL Ludacris SL99 is also not cheap either.