I would prefer always the 100 surfers with 300% prod because that value seems real... 600% prod is very strange and not very usual, not to mention about 3.000% prod (30 clicks).
In your example with 30 clicks per surfer it's most likely to be a cheat. Hope your trade script is able to block those... the mine does
Mathematically both trades would get the same priority to get some traffic from you (assuming you are using the so called pure productivity trade method that most trade scripts use), but most trade scripts will flag excesibvely high productivity as cheat (and usually it is).
In any case... as long as they buy their productivity is ok. Surfers are productive only if they buy