30 x 40 is difficult to drymount since you must do it in sections, and RC papers are particularly problematic for that. That is, unless you have a 40 x 60 vacuum/heat press, which is a very useful item that takes up about as much space in your shop as a small car, and tends to turn into a storage table.
Lacking a vacuum/heat press, if I had to mount a lot of RC's that size I would want to have a decent roller press that could apply the print from a rolled configuration onto adhesive already applied to the substrate.
A vacuum hot press can be good for this, but, if you're dealing with two impermeable materials (RC paper), then there is a danger that the edges of the paper can bond, before all the air has left the print, resulting in bubbles. A roller laminator / mounter has the advantage that the air is all driven out, so, provided the working area is spotless, you end up with a perfect flat image.
We bought our 60x40" Hotpress first, but discovered that we couldn't process aluminium, DiBond or Forex, because of the breathability issues (and because Dibond and forex don't like heat), so got a 44" Jetmounter (we're in the UK, so these are Hotpress branded Drytac products). I'd say we run 95% of mounting work through the roller laminator, and regularly apply HPR and canson rag onto a whole range of substrates.
We often use the vacuum press, after mounting with the roller, to cure the adhesive, when using dibond, MDF etc (heat and pressure makes a very permanent bond). In addition, in the dead of winter (coming in the next few months), we'll use it to pre warm laminates, prints and substrates. One other advantage of a hot press, is that you can use it to remove the moisture from the print and substrate, helping to reduce the chance of curl.
For mounting a 30x40, you'll need at least as much space in front of the roller machine, as bench space behind it, so will also eat into space (if that is an issue).
If I had to pick one machine for mounting it would definitely be the jetmounter.