Both kits are top notch and I've seen good customer support from both companies. I like whipple's heat exchanger better but realistically either will suite the needs of most people on here at similar boost levels, especially on a stock bottom end. You can find better deals on the magnuson so it comes down to personal preference and if you think "size matters".
Thanks. I knew the Magnuson was CARB certified for CA and I looked up and found that the Whipple is also CARB certified for CA. With all our restrictions it is ironic to see both are California companies.