So what are the Cabalist pets ?

The Cabalists class defining ability has to be the pets, known as Simlacrums (Sims for short). Each pet has very different abilities :

Amber Sim – this is your first pet, gained when you first become a Cabalist. You’ll be seeing allot of this guy throughout your career. Amber has the highest hitpoints of all 5 sims and has a handy stun proc which fires semi-regularly. Unfortunately Amber is bugged and will often disappear and reappear somewhere else (warping). This can be fatal if you’re close to agro. Soloing problems aside this warping can be useful in RvR even if it is totally random. Amber’s stun can also be handy in RvR giving your group vital time to run down an opponent of flee for their lives.

Ruby Sim – gained at level 7 this pet is your main RvR companion. This one has a 1,500 range cold nuke as it's primary attack and will melee if cornered, albeit poorly. It's also very handy in PvE especially for soem extra nuking power in groups.

Sapphire Sim – gained at level 12 Sapphire is your main melee pet. He has pretty good hitpoints and attack speed however it’s his lifetap proc that makes him the best melee pet in the game. This fires often and when it does you can see the chunk taken out of the mob’s health bar. Free of Amber’s warping this pet is the prefered choice when you need melee pet.

Emerald Sim – at level 20 you get the Emerald Sim. This sim procs a disease (with snare) and poison (DOT) which makes it a viable choice for use in RvR however it doesn’t match up to Sapphire PvE.

Jade Sim – you’re final pet, earned at level 32, is somewhat of a let down. Possessing it’s own damage shield it dies just as easily as the others due to the damage shield being a very low powered one. It has been given a slight boost in a recent patch but again it can’t match up to Sapphire with even Emerald and Amber being better RvR choices.

So which one is best for leveling (PvE) ?

Personally I used Amber for PvE until getting Sapphire at level 12, then it was Sapphire exclusively. Since then however the Ruby pet was turned from a very weak melee pet into a very handt caster so with that in mind I'd have to say that the Ruby pet would also make a viable choice albeit using different tactics.

How about RvR ?

In RvR I tend to use Ruby the majority of the time with the odd appearance from Emerald for it's disease / snare.

Can I buff my pets ?

Yes you can using the baseline spells gained in the Spirit line however Im of the opinion that it’s a waste of time for a Matter Cabalist. For each fight I prefer to be full up on power and with a 100% healthy pet so I found that I used to recycle my pet often (sometimes after every fight) making any time or power spent buffing kind of a waste.

Can I heal my pets ?

Yes but I rarely do seeing as I recycle frequently (see the pervious answer). Also pet heals seem to pull a great deal of aggro so be careful and avoid if possible.