As far as I'm concerned, they are both the same thing, only one is more 'commercialised' than the other.
Most people celebrate Halloween without being aware of it's true origins...yet still celebrate it because it's traditional.
Exactly like Christmas and the Winter Solstice

I DO celebrate Halloween rather than Samhain though, because I'm not Wiccan. I don't feel comfortable using the term 'Samhain' personally, although I am spiritually connected to the season and I am aware of what it represents...if that makes sense.
Even though I go 'flat out' on Halloween, I
do celebrate the true meaning too; by displaying items appropriate to the season in my home, and reflecting on the year gone by, as well as remembering my family members who have passed on...even though I don't make a 'big' ritual of it.
Halloween is the 'on the surface' fun part, that includes both the participation of myself and of others. Difference is, I KNOW what we're celebrating lol.