UKC

I need to buy a modern compact to relace my loved but very battered Panasonic LX3. I'm considering a Sony RX100 but in the meantime I've got a ski mountaineering trip to Morocco coming up and am considering taking my Fuji XE2 and would like a small and compact fixed focal length lens to put on it. Which one though? The 27mm pancake is attractive from the size and weight perspective, but something a bit wider like the 18mm f2 might be more useful, or? I want it to do everything from landscapes down. I currently have the 18-55 and 55-200 zooms and have no experience of the primes...

I'd go with the 18mm f/2. Can always crop in later and the 27mm wouldn't gain you enough reach to make a difference. The f/2 even at 18mm will make for some ok depth of field with a close subject/big background.

As far as compacts go, I use an x100 and have been happy. 

I have a Fuji and an RX100. I think if I were in your position I would either take the Fuji with the 18-55 and accept the weight, or just take the RX100.

I'd second Robert's suggestion to swallow the weight unless you specifically want to carry a single prime. The 18-55 is pretty light anyway. If you must take a single prime, have a look at the newish 23mm f2. Tiny, light and weatherproof, though maybe not wide enough for you. I have the 35mm f2 and it is very impressive, fast AF too.

Morocco is extremely photogenic... 

I too agree with Robert. Not *that* much weight saving as between prime and 18-55, but if you really want to save weight, RX100.

Thanks for the advice. I want to be abe to carry the camera in my shell jacket pocket, or possibly stuffed down the front of my salopettes as I'm a firm believer in having the camera protected but ready to be used at any moment. The Fuji with the zoom is just too big, hence looking at the idea of a small prime lens which would just work. I don't have an RX100 or similar yet - still agonising over that decision, and was thinking this woukd be a stop-gap measure. Though for the price of Fuji lens I'm close to the cost of a used RX100. Decisions decisions...

Do be aware that the RX100 does seem to be rather easily susceptible to dampness if you are thinking of putting it in a shell jacket pocket without protection. I and others on here have had an RX100 ruined by damp. I don't know whether other non sealed equivalents would be any better though.

I re-married with a fixed 23mm F/2 prime on a Fuji X100F. Over the years, I went from MFT with 17mm/60mm (34mm/120mm FF eq) primes, to Oly 12-40mm (24-80mm FF eq) F/2.8 back to a lens that's 35mm FF eq. I had a DSLR before, but never took it to mountains. I started with film, so I don't find a prime to be limiting factor. 

I used my iPhone 6S+ (29mm FF eq) for a while as my Olympus E-M5 MKII broke three times in a year and I found 29mm a bit too wide. 

My last 8 photos (excluding from the selfie in a bothy) were all taken with X100F and I am loving it. Moving away from a zoom lens, I learnt to pay more attention to the angles and surroundings again. 23mm F/2 prime should be the same as X100F, I am not suggesting you buying one if you can get away with X-E2 + 23mm F/2.  

Yep, I've seen that. Thats why I'm sitting on the fence over an RX100 still. The way I use a camera its likely to get damp.

Have you thought about a Fuji XM1? They are tiny but still with the same sensor as your XE1. One of those and a pancake lens will give you a small package but still good images. Or, replace your LX3 with a newer version (LX5 etc)? I still have a LX3 which I think is brilliant little snapping camera considering its size. 

Have you thought about hiring a lens for the trip?

e.g. http://www.lensesforhire.co.uk/

If I'm just taking one lens, and I want it to feel light, then I always go for the 35/f2.

However,  I'd probably take the 16mm, 35mm, 56mm, 90mm and 55-200 zoom and maybe a fish eye, battery grip and flash.