I would equip them for Combat. While DA veterans are improved Tactical Squads, bolters are a total waste of time, because they're exactly the same as buying a Tactical Squad, only for more points. They can only take 1 heavy or 1 special, making them little better than Tactical or Devastator Squads (the ability to take 5 Marines and a Heavy Weapon is kinda offset by the fact the Devastators will do that for the same price in the early stages, thanks to the Veterans expense).
You could got for a meltagun and x3 Combi-meltas and a drop pod, allowing you to have a shot at taking out enemy armour, like Sternguard. It's a lot to ask, though.
In the meantime, I'd equip them for combat on the basis that they are actually better in Combat than any other Dark Angels unit, bar Deathwing. They beat Assault Squads, due to their additional attacks, so long as you buy a Rhino to offset their movement losses. You could get 8 Veterans with 2 Powerfists and a Powersword for 225 points, and a Rhino would make them 250. 10 man (non-mutable size) assault squad will cost 260 with a Powerfist.
The Veteran Squad gets six Powerfist attacks and throws in 4 powersword attacks on the charge. The regular bullet catching Vets get 4 attacks each, granting you 20 standard Marines attacks.
The Assault Squad gets three powerfist attacks, no powersword attacks, and 27 standard attacks. Meaning you're losing 7 normal Marine attacks (and two wounds), but gaining 7 special attacks. For ten points cheaper.
Obviously, there are considerations such as the Squad and Rhino being 2KP, as opposed to one. There is also the fact you can't assault from the Rhino as well as you could if you were jumping around the battlefield. There is also the point that every Veteran you lose reduces your attacks greater than losing assault Marines. But still, in terms of raw killing power, they're vastly superior.
Alternatively, DA Veterans are a way of returning to the min-max days of 3rd and 4th Edition, when you could take 5 man units with heavy and special weapons. They are vastly inflated in points from the days of old, though, and don't have the advantage of scoring.
Normally, though, I use the DA veterans box to make nice models with Tactical Marines, and to have Sergeants in Rrbes.