The discussion over who has the bigger market and/or popularity is a hard one.
Samsung/Android are bigger and more popular, no argument there. But they sell more variations of price/size/design, so by default they will be highest in sales/market share.
Android's market share in the US is larger than iOS's, but Android's share is falling, and iOS's is growing.
And not only does Samsung have a smaller US market share than Apple, Apple's share is growing faster than Samsung's:
Apple Makes Gains in U.S. Smartphone Market Share
comScore today released the results of its monthly rolling survey of U.S. mobile phone users for the November-January period, finding that Apple's smartphone marketshare rose 3.5 percentage points between October and January, up to 37.8% of both U.S. smartphone platform and hardware sales.
Samsung was second in hardware makers with 21.4%, up from 19.5% three months earlier. HTC and Motorola both experienced significant drops in market share, while LG gained slightly.
Google's Android was the largest smartphone platform with 52.3% of smartphone platform share, down from 53.6% three months ago. Android, BlackBerry, Microsoft and Symbian all lost share, to the benefit of Apple. As a result, Apple and Google control more than 87 percent of the smartphone market.

Notably, comScore's data tracks installed user base rather than new handset sales, making it more reflective of real-world usage but slower to respond to shifting market trends than some other studies.
comScore today released the results of its monthly rolling survey of U.S. mobile phone users for the November-January period, finding that Apple's smartphone marketshare rose 3.5 percentage points between October and January, up to 37.8% of both U.S. smartphone platform and hardware sales.
Samsung was second in hardware makers with 21.4%, up from 19.5% three months earlier. HTC and Motorola both experienced significant drops in market share, while LG gained slightly.
Google's Android was the largest smartphone platform with 52.3% of smartphone platform share, down from 53.6% three months ago. Android, BlackBerry, Microsoft and Symbian all lost share, to the benefit of Apple. As a result, Apple and Google control more than 87 percent of the smartphone market.
Notably, comScore's data tracks installed user base rather than new handset sales, making it more reflective of real-world usage but slower to respond to shifting market trends than some other studies.