Although there have been many sets of radicals and many classifications over the years, the traditional set of 214 radicals is now usually identified with the famous 康煕字典 (Kangxi Zidian). To many people, if you say the radical, it's understood that you're referring to the traditional Kangxi classification.
From that point of view, the traditional radical is 入. See the 康煕字典 online, page 126.
In the case of 全, however, the simplified Japanese 新字体 (new character form) uses 人 rather than the traditional 入, so it's natural for some modern dictionaries to classify it under that instead. I have three paper character dictionaries that use the radical system, and all three place it under 人 rather than 入.
From this point of view, the modern radical is 人.
Of course, it's quite possible for different dictionary editors to classify characters under different radicals. But I think the above is a decent description. As you can see, in this 漢和辞典 published by 学研, both the modern and traditional radicals are listed, corresponding to the modern and traditional forms of the character: