They seem identical down to the documentation:

```
help?> Base.product
product(iters...)
Return an iterator over the product of several iterators. Each generated element
is a tuple whose ith element comes from the ith argument iterator. The first
iterator changes the fastest.
Examples
≡≡≡≡≡≡≡≡≡≡
julia> collect(Iterators.product(1:2, 3:5))
2×3 Array{Tuple{Int64,Int64},2}:
(1, 3) (1, 4) (1, 5)
(2, 3) (2, 4) (2, 5)
help?> Iterators.product
product(iters...)
Return an iterator over the product of several iterators. Each generated element
is a tuple whose ith element comes from the ith argument iterator. The first
iterator changes the fastest.
Examples
≡≡≡≡≡≡≡≡≡≡
julia> collect(Iterators.product(1:2, 3:5))
2×3 Array{Tuple{Int64,Int64},2}:
(1, 3) (1, 4) (1, 5)
(2, 3) (2, 4) (2, 5)
```