Oliver Bennett: On one side, a temple to the aspirational lifestyle. On the other, old-fashioned good value

You have only to see their locations on London's Oxford Street to find out where the two big stores stand. Marks & Spencer is at the smarter, western end, rubbing shoulders with the likes of Selfridges. Bhs lurks by the fast-moving, fume-laden vortex that is the crossroads with Regent Street - an area known to Christmas shoppers as the third circle of hell.

You have only to see their locations on London's Oxford Street to find out where the two big stores stand. Marks & Spencer is at the smarter, western end, rubbing shoulders with the likes of Selfridges. Bhs lurks by the fast-moving, fume-laden vortex that is the crossroads with Regent Street - an area known to Christmas shoppers as the third circle of hell.

Marks & Spencer is a more "aspirational" brand than Bhs, indeed, the very mission statement uses the dread word: "Making aspirational quality accessible to all." A walk into the Oxford Street flagship shows that the green and gold colours long associated with "Marks & Sparks" have survived, but are worn lightly. Patches of the M&S trademark eau-de-nil are on wall and floor, reminding you that you're in the trustworthy, if slightly dull, house of St Michael.

The green has been joined by lots of other spot colours heralding a new range of sub-brands and messages. The sale panels are in red, the holiday shop's "suncare spot" is in orange, the café signs in blue - all clean type on clear planes of colour in the modernist tradition. Although the panels all compete for attention, they've done a good job: the effect is never too busy. It feels spacious, soft, blond, modern: just the ticket for the "aspirational" bourgeois 'burb who shops here.

Equally, the M&S copywriters have been hard at work. Someone's got to be applauded for the pun in the schoolwear section: Top Marks For School. The café is called "Revive" - the ultimate aspirational message to the great 1884-vintage retailer itself. It needs to do just that.

Meanwhile, over at Bhs, one walks under the ugly bright blue fascia with its hand-drawn style logo to be met by a veritable forest of signs. It's M&S that started as a market stall, but Bhs feels much closer to the costermonger's pile-it-high and flog-it-cheap ethos, with a busy, mercantile atmosphere that is less about branding, more about raw sales. Signage is colourful, with a stripey theme that looks uncannily like Paul Smith's old branding, but doesn't have the zoned-out restfulness of M&S. One reason is simple: here in Bhs a soundtrack blares out, so you get Girls Aloud along with spoken adverts delivered in a sing-song airport announcer's voice: "Come to menswear for all your blah..."

The store has lost the cachet-by-contact that it gained by being part of the Storehouse group alongside Habitat and Mothercare, and has reverted to what it always did: give good value to the rump of the British shopping public. After all, when it started in Brixton in 1928, Bhs's proud boast was that nothing cost more than a shilling.

Looking around today, the style remains functional, even old-fashioned. The M&S team would surely have thrown out some of the words in early planning meetings: one banner advertises "Casual" clothes. The café is called "Bhs to go" and offers piles of packets of crisps. An advert for the self-service restaurant, which feels like a corporation canteen, shows meat and two veg, one of them mash.

There just isn't the same house-proud atmosphere as in its competitor. Up in shoes, I see a single child's trainer lying on the ground unattended for several minutes. In M&S, where not so much as a goujon is out of place, they wouldn't allow such a calamity to occur.