Ok, got some time to give a run-down on the Hoff. I'll try and answer this how you have set out your questions however as I do not play Ramos and my only experience with him comes from playing against Mythicfox and his Ramos crew alot of my views come from playing against him.
1. How do they both compare.
Both of them on their own have very low mobility however Hoffman can hitch a ride on any construct that is height 2 so long as they start in base contact. This does give Hoffman a mobility advantage but it is very easy to overextend with a Hoffman crew and end up with no master.
Ramos himself has a ranged offensive spell that will be his primary damage output and does mean that if he is on his own he won't be all that helpless (Armour 2 does help as well!)
Hoffman does not have any ranged offensive spells and his primary damage output comes from machine puppeting friendly constructs to attack. Without a construct near him to pick him up/machine puppet Hoffman is very easy to kill.
2. Pros/Cons.
Both.
Pros : Very good at supporting their constructs either by healing/defence buffing (in the case of Ramos) or removing any bad abilities that they may have (Hoffman with maintain machines)
Cons : Slow, Wk3 and both having low defence
Hoffman.
Pros : Can hitch a ride with any Ht2 construct and then use machine puppet to make them engage.
Can assimilate any LISTED ability on a friendly construct.
The more friendly constructs that are close to him the higher his cast becomes.
Gets rid of bad abilities with maintain machines.
Machine puppet! CB6:rams with critical strike on melee or ranged attack from a construct
Depending on the constructs taken can either make good ones better or steal their abilities and make himself incredably powerful.
Dampening, no blasts, aura's or pulses within 3" of him unless it's his activation
Can gain fast but makes a construct slow.
Cons : VERY crew dependant. If he is ever cought on his own he's dead.
Protected by machines - you can have assimilated armour 6 bazillion that you have just made however if he gets hit you HAVE to take the basic armour of a friendly construct within 3" (Which will usually be 1 or 2)
Close in spell power, longest range spell being combat mechanic (Heal)
No ability to make new constructs
Ramos.
Pros : Armour 2!
One of the highest casts in the game
Counterspell, can stop a spell by ditching cards.
Casting expert. Extra cast action
Can gain scrap as a 2 action.
Able to make spiders and electical creations on the same turn.
Offensive spell that ignores armour
Pneumatic grip
Cons : VERY low DF and walk.
Despite having a high cast his summoning spells need at least a 7tomes to work.
No movement tricks without SnowStorm
Again, crew dependant but can hold his own a little
3. Preferred
While I have the Ramos box he's still unassembled. Prefer Hoffman