For reasons I have yet to understand, some designers have a penchant for putting those
hatches on the foredeck. Personally, on a boat in this size range, I would not want the
hatch there.
We have a PSC 31 with the coachroof-mounted hatch and I would consider it an annoying design flaw if the hatch had been placed on the foredeck as was done on the Valiant 32. Not only would it be a constant tripping and toe-stubbing hazard, it would always be at risk of damage during sail,
anchor,
dinghy, and kayak handling. Furthermore, it would be uncomfortable for anyone lounging on the foredeck, which would not even be possible with the hatch open. Add to this the other reasons previously mentioned, such as greater chance of immersion/leaking from boarding seas, and the foredeck is a poor location for a hatch on a boat of this size.
Sometimes the reason you see hatches on the foredeck has less to do with interior layout than it does the length of the coachroof. On boats with relatively short coachroofs that don't extend very far forward of the mast, a foredeck hatch is almost inevitable. On disproportionately long coachroofs they're almost impossible. On average length coachroofs, the designer/builder may have a choice to do either/or/both. The extra ventilation is nice, but if I were buying a new, mid-size sailboat I'd opt only for the coachroof hatch if I had the choice.
On MUCH larger boats than these it becomes increasingly possible to incorporate a foredeck hatch without all the downsides mentioned above.