While the S2 uses the GN bag shared with the S5, the bag chamber will not allow the bag to inflate to its full potential.  And, as Bud mentioned, the S2 is not a sealed system.  Also, the S2 shares the same motor with the S6 and S7 machines, while the S5 employs a larger motor.  For the same price point as the S2, the S6 is a better constructed machine and it's sealed.  Its only downfall is the use of the smaller FJM bag...

No matter what type of vacuum (paper bagged, reusable cloth bag, melt blown polypropylene bagged, filtered bagless, cylconic bagless and water-filtered) some form of filth will always remain in the machine and in its filters.  We must not forget the attachments and hose which will also accumulate filth, even after one use.

As for vacuums used in the most demanding of situations, those used for dry hazardous material recovery or in cleanroom environments, they all share one similarity - they're bagged...

I, too, could not understand Miele risking it's good name by entering into the low end market to artificially increase sales.

But then I am not one of the avaricious stakeholders of Miele Corp seeking to rape profits in this disastrous doomed from the start Globalization Economy model that has plunged our world into the sorry state it is now in...until I delved into the situation a mite bit deeper

"Review - Miele S2 Series Econo Line Canister Vacuums
The Miele S2 Economy line offers many features found in the S6 & S5 series units at an economical price point meant to attract those looking for an entry level vacuum cleaner.  Missing from the Miele S2 Contour, Miele S2 Momentum and Miele S2 Continuum are the sealed body and bag compartments.  This is vital to ensuring true sealed HEPA filtration which cannot be offered on the S2 models.  The Miele S6 and Miele S5 canister models also offer more robust plastics to ensure durability and performance."

This last statement pretty much asserts that Miele believes - and trusts - that the bumperless thin plastic carcases will fail quickly and perhaps they believe that this will drive the majority of owners to upgrade? I don't think so...

It would not surprise me to learn that Miele has sub-contracted the manufacture of the S2 to the PRC.

A long standing, successful and well-respected Vacuum Cleaner Dealership in London Ontario Canada is McHardy Vacuum; they pull no punches comparing the S2 to the rest of the Miele line-up.

Entry level? The S2 Contour retails for $499.99 at Sears Canada while Costco has it listed at $399.

Canadian Tire has the S2 Momentum for $599.99 while Future Shop will sell you either the Contour or the Momentum for the above prices.

From a quick Canadian survey it would appear that the S2 is not available at Miele vacuum Shops but being dumped at the Big Box stores here.

I smack my forehead at the gullibility of the uneducated consumer.

I also noticed that in Canada the Dealership's Contour and Momentum models are in fact the superior S4. Some hapless folks will be confused by the same model names and flock to the Big Box for a perceived 'deal'. McHardy does indeed guarantee to match any other price but since they don't sell the S2...well, Miele is doing legitimate shops a dis-service duplicating the model name on two decidedly different quality machines. Meile Canada will say it is not competeing with Vacuum Shops but they are engaging in deception through mis-direction.

This blog comment pretty much sums up the important differences -

"needs to be a simple, reliable work horse,store compactly, do its job well. would like on-board storage. do not want electric wand/telescope. will buy parquet floor attachment.

miele- s2 Olympus- cheapest, lightest while using the largest bag. i really thought this was a perfect first vacuum but it lacks on-board storage and does not store upright/compactly. made in china? skimped on finish and uses lesser quality attachments, uses the largest bag but is it able to fill it up within the compact canister?

s5 ariel or pisces- basic s5 models. hepa filter, non electric wand, uses largest bag and stores compactly. finish and quality of materials is better than the s2 class, but is it more than $200 better quality/materials vs the olympus?

skipping the s4 group b/c they use a smaller bag but is midsize?

The Public at large is not as universally stoopid as Miele could hope!

Dave

Costs are reduced as the S2 is made on a fully automated assembly line at Miele's plant in Bielefeld, Germany.  This vacuum is NOT made in China.

The S2 is an excellent vacuum in the department store setting.  While it is not sealed and has a reduction in components and less plastic, it still retains high-quality components and Miele's in-house manufactured motor.  Truth be told, it's probably one of the best built vacuums available at a department store in Canada.

Canadian Tire's S2 Contour is $100.00 more because it comes standard with the STB 205-3 Turbobrush.

I own a S2 Momentum and while it is not my favorite machine out of the ten Miele's I own, it still is an excellent vacuum.  While not as refined as other Miele's, it does exactly what it was designed to do and does it well.

The whole Contour, Momentum and Continuum names through multiple lines does get rather confusing, though... 

Well I finally sold the S2111 I had. I couldn't wait to get rid of it.  Another couple of weaknesses soon became apparent with this vacuum compared to the better S5:

1. The hose on the UK market ones measure 1.5 metres compared to the Miele standard of 1.8 metres making this kind of machine more liable to knock me into the back of my ankles when pulling the machine along.
2. The two fixed height (non-adjustable) suction pipes that have to be locked together level out to be around 113cm in height. Much prefer the telescopic adjustment and the tubes have a daft lock storer nib located behind the handle to lock one of the tubes together when not in use for storage - the last time one of them fell off and hit me in the foot was the last straw!
3. The noise level is higher due to a lack of sound insulation.
4. The cord rewind doesn't fully rewind all of the cable back in, merely only going in ever so slowly compared to the fully continuous rewind on my S5211.
5. The tool storer option to go behind the handle has been retained though it would be better if the design could be locked in the other way with tools directly under my hand - otherwise some of the tools fall off and when not in use, the nib *though supposedly turns around to the bottom away from the owner - seems to catch the cuff of my jumper sleeve when the vacuum is being handled.
6. The cheap floor head that comes with this vacuum cleaner isn't as well built as the standard metal soleplate version with the S5.