We remember the KISS principle - keep it simple. ..

Ive lived by that in my later life and while expanders/ slide outs have their benefits, there is always negatives.

Extra weight, as stated fragile mechanisms, purchase price and so on. But there is also one aspect that would turn me off...complexity. That KISS principle is relevant. Its the same relevance as pop tops to me. Replacement/cleaning/flapping of canvas, raising to make a coffee, latches. 

Ok, there are also good reasons like a low carport/garage. With slide outs, a short carport could be used. 

Just my view but each to their own.

Tony

The Expanda type of caravan has all the disadvantages of a poptop, but the advantage of extra room once it is opened up. It will be heavier that the equivalent (expanded) length poptop. Both regular poptop and the expanda are heavier than the equivalent full height caravan.

It all boils down to your intended use. The poptop type (including Expanda) vans have a lot less thermal insulation, and are therefore less comfortable for winter usage (and even extreme summer usage as well). In heavy winds, the roof may move around a bit. The roof has to be raised when setting up and for some people this can be a problem. They must be thoroughly aired out and dried before storing away, or mildew will result. Often, the switches for the lights are in the roof (at the light itself). This is a downer for short people. The resale value of poptop type vans is much lower than a full height equivalent.

However, they are much better to tow. The vents in the canvas can be opened up in reasonable weather and you have excellent ventilation. The centre of gravity is lower - more stability against crosswinds or buffeting by trucks as they pass you. Less fuel consumption for a poptop type van. You can park them under a lower garage or carport as well.

I have a 16.5 ft Jayco poptop van, and the height of the van is marginally higher than my Pajero. Result is that the fuel consumption is very good, and for a long trip eg around Australia, this is important. This is ideal for my usage - we rarely do less than 1000 km for any of our trips. If you are only going to take the van to the beach for 3 weeks each year, I would go for a full height van.

K.I.S.S.

Only way to go. Keep it simple.

The "Technology" for Slide Outs/Expanders is pretty basic but lends itself to jamming and not opening/closing properly. Saw one guy whose slide out wouldn't close properly. Tried quite a few times to open it up fully and then close but it always sent it back in slightly out ,so it was lopsided. He tried assisting the side that wasn't going in properly and it still sat out of line. Quite a few expletives and quite a lot of silicone spray and it finally retracted evenly.

I expect there are lots of vans out there that never have problems But for me forget it.

 There seems to be a bit of misinformation above. For starters, people seem to be thinking that Expanders only come in poptops.  Jayco Expanda 16 & 17' models come in both pop-top and full height, the 20" model only comedfull height. The OP introduced the subject bu saying expxnda and not Expanda, was that a spelling mistake or does he recognise that other manufacturers make expanding vans? New Age and Windsor produce expanding vans, some New Age models are full height.

The weight depends a lot on the construction and inclusions. The Expanda pop-tops are about 100 kg heavier than the samdfloor layout full height van.  Also the 18' Jayco Journey (full height) has a tare of 2010 kg,  the 18' Expanda pop-top tare is 1990 kg. You get far more space in the expandafor less weight than the Journey.

As regards to the lack of insulation, there is far less heat loss than the pop-out camper trailers with the same floor space.

"Jayco Expanders don't have a slide out mechanism," the 20' model does, the lounge slides out, so that statement needs qualifying (nit picking.) There was one manufacturers where the beds were in slide-outs with insulated walls but i can't find them, I think it may have been AVAN, who I don't thinlproduces them now.