Terminators can have assault cannon, specialized missile launchers and heavy flamers. In most ways they are more limited in weapon choices than devastators especially when one contemplates the variety of special ammunition many weapons have available.

Slight necro, but topic is still relevant, and show in any search about Devastators.

About Dead Station Vigilant and shooting; one of my players, a shooty Tac Marine with Bolter Mastery and Astartes Weapon Specialization (bolter), and he loves it.

- Main ability of DSV allows choosing one of 4 bonuses; among them, additional damage when Shooting (and not a +1, it's usually from +3 to +6!) or additional Cover (especially if it's doubled by Dig In) are amazing. Additional Cover also works for entire Kill-Team in this cover, which allows some serious fortifying! While it's Intelligence-Based, even with fairly low 40-something Intelligence this class is amazing.
As additional bonus, Devastator can now help other with things like Lores, especially one shining new Lore that I do not want to spoil for players, but it's cheap and available at +20 easily. There are also some other Lores, one Peer if I remember right, and Wisdom of the Ancients. It also has very low requirements and entering this Specialty is cheap, while advancement table is fine.
- If Devastator is Squad Leader, new Oath is amazingly powerful in some situations and especially in high-level missions, where your players usually have a lot of Insanity stacked, especially on Outer Reaches, it's a mine of Insanity, Corruption, and salt y players. New Squad Modes are also super-hot. Even if he's not the leader, Living Death can be amazing. Kill-Switch can save entire Kill-Team on occasion. Also, new Demeanour, more Roleplaying possibilities!
- Additional abilities against Outer Reaches threats comes in handy, quickly, if your campaign has even some elements from Outer Reach.

Shooty and Intelligence-based characters should definitely pick this Specialty. Even those with lower Intelligence can take it and rise their Intelligence in time.
Just take notice, this Specialty, if done right, is very powerful; as a GM, you should consider giving it to the weakest member of the Kill-Team, relatively speaking; in hand of a well-rounded character it can easily overshadow others in combat with right gear.