Gas vs Diesel

Diesel heaters can be noisy, especially older models. I'd go for the Truma, given a choice.

I don't know about the Dometic vacuum toilet but people have found Dometic toilets in general to be troublesome.

It's not an AutoSleeper Nuevo then.😀

PS. Bear in mind that if you buy a MH with more obscure fittings, spares are going to be harder to come by and repairs may cost more.

I have a lot of experience of diesel heaters - but in boats - not caravans / motorhomes.  In my opinion Eberspacher is far more reliable than the other main contender - Webasto.  That said, as Tinny has pointed out, they are noisy, especially on start-up and whilst you can get away with it in a marina etc, they could be a bit antisocial in the more confined space of a caravan site.  The other thing - is the constant ticking of the fuel pump - again it can be quite obtrusive on a high setting but not so bad on tick-over. How effective they are depends on the installation of the ducting and that applies equally to diesel heaters or their gas equivalent.

As far as toilets are concerned - if I tell you that five months into ownership of a high-end Knaus Starclass, I got the dealer (at a great deal of expense to me) to change the standard Dometic toilet to a reliable Thetford after the Dometic had a problem with it every time we went away.  I just cringe at the thought of a Dometic vacuum toilet - just how many opportunities there would be with that for it to go wrong! I'm far from alone in my experience, either.  The internet is littered with other owners complaining about Dometic toilets letting them down in one way or another and I know of two other people - who on my recommendation - went to our dealers to get their Dometic swapped for a Thetford. If you take my advice - stick with the Thetford.

We had an Eberspacher in our first Autosleeper it seemed like a great idea and did cope well off grid but we found it noisy (we did try to reduce the noise but to no effect) and the van was either warm or cold, there was very little in residual heat, no quiet background warming. In the end we stopped using it and bought a convector heater and enjoyed warmth and quiet. We made sure our present van had a gas/electric truma heater, equally adaptable and only slightly noisy if the fan is used. 

richardandros wrote "they are noisy, especially on start-up and whilst you can get away with it in a marina etc, they could be a bit antisocial in the more confined space of a caravan site"

Marinas are more cramped than campsites. You don't get 6 metres between berths although you can hear an Eberspacher burbling away much further away than that.

Dometic toilet? Better buy yourself some Immodium as a backup. 

A Truma 6e Combi has a massive punch if set to 'gas only' or 'mix 2' and will have the van warm really quickly. With gas generating so much heat, the fan can spin at a fast rate and heating ducts will be blowing stacks of hot air in a few minutes.

when compared to running electric only, the heat is only a third of the above and the fan is restricted to this proportionately even with control panel set to HIGH (if it blows the air too fast it won't be hot and will, in effect, cool the van...

others will know far more about diesel heaters but my reading tells me they take longer to warm up....but the 6e version should have plenty of power and it also has the same 900/1800 w electric function.

the main consideration might be fuel source....diesel is still plentiful whereas lpg is perhaps a little scarcer...where you tour might also affect this as LPG is widely available on the continent.