Minimise the count of prime factors through insertion Given two positive integers A and B, return the position p that minimises the number of prime factors (counting multiplicities) of the resulting integer, when B is inserted in A at p.
For example, given A = 1234 and B = 32, these are the possible insertions (with p being 0-indexed) and the corresponding information about their prime factors:

p | Result | Prime factors         | Ω(N) / Count

0 | 321234 | [2, 3, 37, 1447]      | 4
1 | 132234 | [2, 3, 22039]         | 3
2 | 123234 | [2, 3, 19, 23, 47]    | 5
3 | 123324 | [2, 2, 3, 43, 239]    | 5
4 | 123432 | [2, 2, 2, 3, 37, 139] | 6

You can see that the result has a minimal number of prime factors, 3, when p is 1. So in this particular case, you should output 1.
Specs

If there are multiple positions p that minimise the result, you can choose to output all of them or any one of them.

You may choose 0-indexing or 1-indexing for p, but this choice must be consistent.

A and B can be taken as integers, strings or lists of digits.

You can compete in any programming language and can take input and provide output through any standard method, while taking note that these loopholes are forbidden by default. This is code-golf, so the shortest submission (scored in bytes) wins!


Test cases

A, B -> p (0-indexed) / p (1-indexed)

1234, 32           -> 1 / 2
3456, 3            -> 4 / 5
378, 1824          -> 0 / 1
1824, 378          -> 4 / 5
67, 267            -> Any or all among: [1, 2] / [2, 3]
435, 1             -> Any or all among: [1, 2, 3] / [2, 3, 4]
378100, 1878980901 -> Any or all among: [5, 6] / [6, 7]

For convenience, here is a list of tuples representing each pair of inputs:
[(1234, 32), (3456, 3), (378, 1824), (1824, 378), (67, 267), (435, 1), (378100, 1878980901)]
Husk, 16 bytes

§◄öLpr§·++⁰↑↓oΘŀ


Expects input as strings, try it online!

Explanation

§◄(öLpr§·++⁰↑↓)(Θŀ)  -- input A implicit, B as ⁰ (example "1234" and "32")
§ (           )(  )  -- apply A to the two functions and ..
  (ö          )      --   | "suppose we have an argument N" (eg. 2)
  (    §      )      --   | fork A and ..
  (         ↑ )      --     | take N: "12"
  (          ↓)      --     | drop N: "34"
  (     ·++⁰  )      --   | .. join the result by B: "123234"
  (   r       )      --   | read: 123234
  (  p        )      --   | prime factors: [2,3,19,23,47]
  ( L         )      --   | length: 5
  (öLpr§·++⁰↑↓)      --   : function taking N and returning number of factors
                            in the constructed number
               ( ŀ)  --   | range [1..length A]
               (Θ )  --   | prepend 0
               (Θŀ)  --   : [0,1,2,3,4]
 ◄                   -- .. using the generated function find the min over range