Ok well it's less of a comparison and more of my experiences of using a soft flask products.
Hydration is a topic of conversation (and opinion) that can fill a whole day of running in the trail running community and even then there is no definitive as someone will inevitably throw another opinion or view in that is just as valid as all the others that came before it. How, when, with what you like to fill up the water tank on the go really is a matter of personal preference and so what I can confidently make reference to is my own experiences and preferred watering methods.
I don't drink a lot on the run, I'm almost embarrassed to say, I simply find water boring, I'll almost go as far as admitting that I don't like the taste of it, but, there is no taste, so not a valid comment. Nonetheless, its' life saving properties have me reaching for it when my thirsty body insists and so the next task is to get the right equipment for use on the run.
I've used hydration bladders during the early days, however they are simply not a preferred bit of kit not for me, I find them cumbersome and inevitably, as full at the end of the run as they it was when I started. Bottles have always been my preferred choice. I've persevered with them in hand and in packs. There is a new wave of hydration products that has come into fruition and I'm sure that most folk by now have tried a soft flask.
I was excited about trying my first one and knew immediately that I'd probably never carry a bottle again. The first one I tried however lasted half a dozen outings before a leak in the plastic revealed a weakness with the product. Nonetheless I wanted to persevere as I liked the concept so much. I subsequently obtained a couple of NDURE's version of the soft flask and have been using them since.
They have a range of sizes of soft flask from 148ml (5oz) through to a 500ml (17oz). They even have soft flasks with straws if a straw is your thing. I have teamed an 11oz soft flask with an Inov8 Race Ultra 0.25 hand strap. Interestingly you don't need to grip the flask in the hand strap as the strap holds it firmly into your hand. The flask itself has a grippy texture and consequently no slipping. When I was scrambling over large rocks in Cyprus's Avgas Gorge and needed two hands, the durability of the plastic body of the flask was put to the test. Inadvertently I slammed it into rocks whilst using my hands to haul myself over the rocky outcrops. It survived, although I wouldn't have wanted to push my luck repeating the action too many times.
Usually when you are in the peace and quiet of your run, there is the inevitable sloshing fluid noise from your backpack or hand held to keep you company. Yet the flask boasts it's compression the emptier it gets and in doing so, eliminates the sloshing and jiggling.
I have not been disappointed in how it performs in a race vest or pack either. If there is a securing system to hold bottles in place on your backpack, then the flask performs equally as well as bottles. Certainly the large mesh pockets on my race vest were too big to hold the flask alone, which is slender and minimal. The simple design is comprised of a plastic body and the bite valve. That's it, no fussy locking systems or extras that are simply unnecessary such as a valve covers. This flask did not leak it's contents as the valve alone acts as the locking system. My ultra race vest has elastic bungee's attached inside the pockets and i simply hooked this around the hard plastic neck of the flasks valve, this keeps it firmly in place and on the go it's a matter of unhook and drink, no fighting to squeeze an over sized bottle in to a under sized pocket. Not once has a flask fallen out. When empty it packs down and weighs nothing. I usually refill in streams if I run out of water and found it a fuss free experience with the flask and no different to filling a bottle. There is no complexity to removing the bite valve, it's simply a case of twist, fill and go.
When it comes to cleaning: the flasks have a fairly wide neck opening which enables you to get a small brush inside. This is important if you use the 5oz flask (for example) for gels or other gluppy fuelling substances.
Overall then, what I like about the soft flask is it's ease of use, no bulky bottles digging in ribs or collar bones. No twisting or pulling on bottle mouth pieces, just bite the value and you're hydrating. It's impressive compression when empty and that it is a crowd puller amongst the rambling fraternity. The real crunch though comes when considering it's cost effectiveness and the price is possibly the most reasonable on the market, for example the 500ml flask is priced at EUR 16.95 the equivalent of £10.55, cheap as chips, for a product that does the job as good as any on the market at the moment.
If there is anything to consider: then there may be some merit in adding a feature to assist in grabbing it out of a pack and/or allows it to be secured into a pack. During test there has been the odd occasion (as the flask becomes empty and I'd stuffed if further into the pocket) where it was taking longer to get the flask out of the vest pocket as I had to fish around for it. A grab strap for example would assist and smooth the process. Would this be an unnecessary feature I talked about earlier I don't know?
In addition, I've tested NDURE's 250ml Hydra cup on the go and whilst it's relatively small it's a handy bit of kit when water is in ample supply and you don't want to carry bottles or flasks. Certainly I've folded it down and put it in the zip pocket of my trail shorts and got it out when I've needed a sip on route.
If nothing else it'll satisfy a kit list item of having to carry a cup i.e on Mountain Marathons as it packs down to post it note size.
What ever your preference these types of products are worth a test at least as in my view hydration systems are becoming more sophisticated and these guys are listening to the needs of the runner and responding with great products. Thanks NDURE. You can visit their website to view their other treats here: no here, haha, got ya.