You don't always have the option to allocate the wounds the way you'd like. You can put the victim up front, but mobile firepower or barrage weapons can get the hits coming in from an unfavorable direction. This assumes squadroning, which I would not do for a mixed load squadron.
IMHO the double weapon speeders need to be in separate slots on the
FOC.
If you are running a single speeder, doubling up on the weapons is a good idea. Running multiple squadrons of the same double weapon seems overkill (barring specific situations, like apocalypse games)
I'm an Ultramarine player. I've got
TAC, multi-role flexibility hardwired down to my gene-seed. Hyper-specialization is for Xenos. I enjoy the classic
MM/
HF tornado.
Warning: stream of consciousness rambling ahead as I think about the issue.
With mixed squads, you end up with half the squad acting as cheerleaders while the rest does the work. I'm not fond of this practice. But the cost of a (
MM/
MM +
HF/
HF) squad is the same as a (2xMM/
HF) squad it's not an issue of wasted points. The points are wasted (or invested in flexibility) anyway. Is it better to spend points on wargear of models? In an ideal situation, having the weapons doubled up will let them get into the perfect position. Point for the 2x. If you have the
FA slots, double weapons let you get the ideal weapons to the ideal targets at the same time. Also point 2x. But lets think about the actual table, and not the theoretical one. You can't guarantee that the right speeder will live. Their very nature demands aggressive deployment, so it will take minimal effort (if any) to get some guns pointed at the one you want to live to shoot it down first. Point mix. This is where the redundancy of the mixed speeder comes in. If only one lives, it's going to have at least one of the right gun left to do the job. Also, if you are just fielding one, mixed is the way to go for most
TAC lists. Sidebar: Vulcan makes the
MM/
MM redundant with TLing (how much melta do you need to pump into the side of a tank?) But
TL'd
HF/
HF is just going to make troops evaporate. Still,
MM/
HF is probably the go-to for salamanders. Mechanically, I'm calling this a wash. 2x speeders look to work better in ideal circumstances, but I think on the table, I like the redundancy of the mix. This is our normal risk/reward evaluation. 2x speeders have a higher potential in ideal circumstances, but perform worse in bad ones. Mixed lack the high end, but also the low. Aesthetics? Both look about the same, no preference. Fluff/tradition? Mixed gain points here. Practicality? I'd have to see what a modern speeder kit comes with, as mine date to 3rd (or older) magnets probably make this a non-issue. Other options?
HB/
AC/TML? The
AC might have a place in this discussion, but lets not muddy the waters. Don't like them on speeders anyway. Looking ahead,
DA pay the same price, so unlikely to change in the new codex. Situation is stable.
FW experimental rules are paradigm shifting for speeders, but we'll cross that bridge once we get to it.
TL
R: I warned you not to read it, my opinion was in the first few lines.