Samsung 50-150 vs MFT equivalents

Warning - long post!

So, I've been planning for a year or so to buy the Samsung 50-150 f2.8 S. This is a bit difficult because it's not readily available in any country I've visited, and I'm reluctant to order internationally because of the general hassle and import duties, but I think next month I'll finally have the opportunity to buy one. However, now I'm starting to wonder if the Panasonic or Olympus pro zooms for micro four thirds are a better buy. I'm posting here in the hope someone will offer advice.

More info: my main camera is a NX30, which I'll upgrade to the NX50 or the NX1 at some point. I currently have a Panasonic GM5 and my girlfriend has a Panasonic G3. I have no real interest in any other cameras, so I can be fairly confident we will always have both a Samsung NX camera and a micro four thirds camera as long as both continue to be produced or there is a drastic change in the market. All my current gear is listed in gear list below. The main use for this is low light photography (events, special occasions, general travel photography in the evening, including tripod use). I don't expect this to be a main carry everywhere lens, I doubt it will make up more than 15-20% of my total photography. But I am definitely sure I want one of the three - there are time over the last 2 or 3 years when I've missed shots because I don't have a good low light lens longer than 90mm (equivalent).

So, options?

I'll list the spec with b&h prices for comparison. Actually I'll have to pay substantially more in Asia, particularly for the Samsung, but it's a starting point. Money is not a big issue but this will be the most expensive single photography purchase I've made so far, so I want to get the right one.

• Samsung 50-150 f2.8 - weight 2.02 lb (.92 kg), price (B&H) $1,599.99

+ better image quality with the Samsung cameras than any MFT camera
+ better low light performance with the Samsung than any MFT camera
+ seems to be best build quality / feature rich (focus limiter, iFN)
- most expensive
- largest / heaviest
- hardest to obtain, hard to service if something goes wrong (because of Samsung's weak market presence)

• Olympus 40-150 f2.8 - weight 31.04 oz (880 g), price (B&H) $1,499.00

+ longer (effective) zoom range
+ has a 1.4 tc available (this is a really big plus as I will likely never buy a super tele lens, so it gets me a 300 (600mm equivalent) f4.0.)
- requires an Olympus body for stabilization (not a huge negative as I want to upgrade the G3 fairly soon anyway, but still not ideal as it means a third UI to get used to, another set of batteries and chargers, etc. etc.)

• Pansonic 35-100 f2.8 - weight 12.7 oz (360 g), price (B&H) $1,197.99

+ cheapest
+ lightest / smallest (by a very large amount)
- no tripod mount

So, can anyone think of any pros/ cons I've missed, or give any general suggestions? I'm posting here because outside of the samsung forum no one will have heard of the NX 50-150, and 90% of replies would be recommendations for the Olympus.