U2, Wembley Stadium, London<br/>N-Dubz, Opera House, Bournemouth

U2's 360 tour flits, meekly, between old hits and tracks from the current, rather lame, album

Is it a crab? Is it a spaceship? Is it a physical representation of the ego of Bono Vox? Whatever it is, it dwarfs the borough of Brent, almost reaching the Wembley arch. Everyone has their own theory on exactly what U2's much-discussed stage set actually resembles. For me, it's one of those claw-like grabbers from a machine in a seaside arcade. The ones that hover tantalisingly over some leftover piece of pop-cultural detritus from the semi-recent past (a Flat Eric, a Teletubby, a Bart Simpson if you're lucky), then deliver nothing.

Yeah yeah, Cheap Metaphors R Us. But if you could drag-and-drop your ideal U2, which would it be? The earnest, scuff-booted youths of Boy? The stetsoned authenticists of Rattle & Hum? The late-comer ironists of Zoo TV? The global statesmen of the past decade? Probably not today's corporate pimps for BlackBerry, whose streetwalkers accost you the length of Bobby Moore Way, but hey.

Personally, I'd take a mischievous Macphisto with a soupçon of "The Unforgettable Fire" sincerity, and it's that song which provides the only real shivers of the night. That was the last time U2 tapped into the dizzy mystery of their one-time peers – Associates, Talk Talk, Blue Nile – and a glimpse of an alternate U2 that could have been, if they'd stayed away from the bloody cacti.

Most of the time, the 360 tour flits between the familiar hits and current album No Line on the Horizon which, once you've stopped sniggering at the drug innuendo of the title, is pretty lame. Bono tries so hard, bless him, in his leather jacket and Gucci shades, desperately trying to match the Dylans and Lou Reeds and Patti Smiths on his shoulder with lines about feeling "like loose electricity while the band in my head plays a striptease", or dropping in ad-libs from Primal Scream's "Movin' On Up", Frankie's "Two Tribes" and The Clash's "London Calling" in an attempt to recoup some cool-by-association. "I think something special could happen tonight," he says optimistically at the scene of his big mulleted Live Aid moment, but it never quite comes.

The stage, at least, is fairly cool. Not quite as sci-fi in the flesh as it looked on Wossy, but the giant mirror-ball effect is quite something, and it's undeniably a step forward from Bowie's Glass Spider, which I saw in the old Wembley two decades ago, whose legs resembled eight scaled-up lengths of mobile disco rope light.

Its sheer scale allows Stumpy Hewson (as you can see, I've remained untouched by the Bono charm offensive which has muddled the judgement of other, usually reliable critics), his garden labourer on guitar and the Other Two to play so far apart they may as well be on separate continents, their wanderings assisted by moving radial walkways. Give it a couple of tours and they'll be Stannah stairlifts.

The "special" moment almost arrives. "Sunday Bloody Sunday" sidesteps Partridge-based hilarity by being updated into a tribute to detained Burmese politician Aung San Suu Kyi (complete with masks). Then Bono blows it all by leaving us with "Moment of Surrender", which boasts one of the worst lyrics in living memory. Ladies and gentlemen, I give you: "I was speeding on the subway through the Stations of the Cross ..."

At first I was afraid, I was petrified. It was 8.30pm, N-Dubz stage time minus one hour, and the street leading to the Opera House is already like a scene from Shaun of the Dead. Booze-battered blokes stagger around paralytically, on a knife edge between picking a fight and wetting themselves. The faint whiff of menace is in the air.

Then it dawns that these zonked-out zombies are merely the background noise of Bournemouth at the height of the holiday season, and N-Dubz's actual crowd is the far younger, more excitable throng outside the doorway, hyped up on alcopops, turning cartwheels and yelling at the stewards. I experience a Burchillian glow at the sight of "my people" enjoying themselves (in the knowledge that, were I the same age, they wouldn't be "my people" at all). What's not to love?

N-Dubz hysteria has spread far beyond the London borough of Camden whose NW1 postcode provided their name, and reached kids with yokel burrs in places like Bournemouth. I use "kids" advisedly: this audience is barely too old for panto. The reason why, with the exception of the self-fulfilling prophecy "Number 1", N-Dubz singles invariably stall outside the Top 20 is because nobody over 20 buys them.

The man fronting their rap-soul fusion, which resides at the far "pop" end of the grime spectrum, is Dappy, aka Dino Contostavlos. He is also the group's prime scream-bait, despite the handicap of that Peruvian hat which makes him look like he's trying to smuggle an Easter egg. His songbird cousin Tulisa and co-rapper Fazer complete the trio.

People of Greek origin making music of black origin? (N-Dubz won a Mobo this year.) It may strike some as a bit Ali G, but having lived in the vicinity of Camden for 20 years, I know it's the most natural thing on earth. The subjects they rhyme about – untimely deaths, untold amounts of weed, shagging – are the authentic chitter-chatter of the N29 night bus.

There's also a little poison – on one song, Dappy disses a "bisexual prick" and blames him for spreading Aids – but a little marketable homophobia never did Eminem any harm. Despite this, it's all strangely family friendly. There's a bit of larking about in boxing robes to the "Eye of the Tiger" riff, and Dappy gets the crowd to chant "Fazer is a plonker". They stop just short of soliciting a "He's behind you!!!".

Whatever your preconceptions, N-Dubz's urban panto is fun for all ages .... Oh yes it is!