Both are std chicom mills from a well known decent supplier.
Both supply a decent taper ie MT3/R8 in a very light weight package 220/320 kg.

Both will work ... as to how good what are your expectations.
You are NOT going to be putting out full depth cuts with either one at full speed 2 HP power levels in steel with either one. But then again, with cnc, you dont need to.

Also, cnc conversions vary greatly. Everyhitng from 1 micron real world resolution to whatever.

What are your needs ? (In steel).
The limits on both are going to be MRR or Material Removal Rates. Working within the limits of the rigidity of the machines, both can do good work.
More rigid is better. Heavier is more rigid and vibrates less.
A very good Bp M-head is 900 kg for 3/4 Hp, and can fully utilise that.
A very good BP Series 2 at 1400 kg with R8 is 3 Hp and can fully utilise that. Forget about it on a 320 kg desktop minimill.

So it depends. You have not supplied at relevant information.
Also, milling a lot is relative.
10 kg of swarf per day. 50 kg. 100 kg ?

Deep cavities, like 80 mm deep pockets in steel, and bottom surface quality is important ? Or not ?
So You see it depends.