G'day Laura,

Yes, this would be suitable to revive the waterproofing on your Merrell Moab Shoes as they are best used with Leather and Gore-Tex. 

G'day,

Given the boots you've mentioned are a synthetic (fabric) upper, this product would do the trick.  Nikwax is water-based so it won't affect the breathability of the boot. Just make sure to read the instructions before using & you'll be fine.

G'day Walter,

We don't sell La Sportiva so don't have any immediate experience with these shoes - after a quick bit of research, I cant see why they wouldn't work on the TX5 GTX with that nubuck and canvas style tight weave fabric.
The Akasha look to be a different story, being a porous & breathable, non-gortex synthetic trail runner.  I don't think there's really much you can do for those, but there's no harm in giving it a go.

G'day Craig,

Yes based on your description the Nikwax Fabric & Leather Proof should do the trick to add some more water repellency to your synthetic boots.

G'day Tricia,

The Fabric & Leather Proof is designed to revive your struggling footwear, so if your shoes are new we'd say there is no need to use this, however, if you've had them for a while and they're leaving your feet a little damp then yes you could use this to revive them.

G'day Huntzman,

I've just chatted with our footwear experts and we think you'd be ok with either, but the Nubuck and Suede Proof is probably a slightly better choice as the leatherproof might alter the colour/finish or your suede.