M205 is an excellent product.
The blackfire polish is similar to Menzerna 106FA (SF4000) super finish. This product is super easy to use, has a long working time and finish's brilliantly on just about every paint system.
M205 is probably a tad more aggressive in its cutting/cleaning ability. But for cleaning up compounding haze, both products are more than up for the task.
I actually love both of these polish's (205 and SF4000). If i'm doing a 1 step polish I would probably reach for 205. If I was using a finishing polish I would reach for the Blackfire polish. The blackfire polish probably finish's down clearer on softer paints as 205 can be somewhat aggressive on soft clear coats.
This is a situation where buying and trying both products for yourself is the only way to get a feel for which one you like. Both are designed for the same task and work equally well.