Both auction houses had taken parallel gambles to secure headline-grabbing entries for this season's evening sales but they largely paid off.
Claude Monet's 1873 canvas Le Pont du Chemin de Fer à Argenteuil was Christie's biggest ticket on May 6.
High Impressionism has been overshadowed by 20th century painting in recent years, but this cerulean blue landscape of a Parisian suburb bisected by locomotives on an iron bridge was a seminal work for Monet who produced only three other comparable paintings of the subject.
During the last Great Art Boom, in 1988, it was sold by Stavros Niarchos, the Greek shipping magnate, at Christie's King Street for £6.7m - at the time it was the second-highest price ever paid at auction for a Monet.
It proved a solid long-term investment for dealers the Nahmad family who had held it for 20 years - and a risk well taken by Christie's who guaranteed their vendor a price thought to be around $34m.
A buyer bidding by telephone beat out two other contenders to pay a record $37m (£18.8m). The previous auction record for a Monet was the £16.5m paid last June at Sotheby's Bond Street for a 1904 painting from the Waterlilies series.
Sotheby's were selling a Cubist painting by Fernand Léger at their equivalent sale on May 7. Etude pour La Femme en Bleu, 1912-13, was estimated to fetch $35-45m and believed to carry a guarantee in the region of $38m.
The canvas - deemed one of the last major Cubist pictures in private hands - came from the family collection of German silk manufacturer Hermann Lange, who bought it in the late 1920s in Berlin. Bidding was thin but two buyers took it to its low estimate of $35m (£17.8m) or $39.2m with premium, a price at which the auctioneers could probably break even on the deal. These days not even a $35m sale is necessarily profitable.
As global economic gloom descends, the gulf between the best and the rest just grows ever wider as secondary works by major artists proved much more price sensitive.
In all 14 out of 58 works failed to sell at Christie's and if the sale hammer total of $246m (£124.9m) was the auctioneer's third highest in the category then it was also well shy of the $287-405m global estimate. Four of the unsold works carried guarantees (undisclosed sums promised to vendors regardless of the outcome of a sale) including Christie's Kees Van Dongen's Anita en Almée estimated at $12-16m.
Sculpture, that in relative terms was once undervalued, was the focus of the most competitive bidding. An exceptional group of Giacomettis from various periods included Grande Femme Debout II, a trademark 1960 bronze sold to the Gagosian Gallery at a record $24.5m (£12.4m), a record price for the artist. Christie's had thought it would bring $18m, but there were seven serious bidders.
Rodin's Eve, conceived in 1881 for the Gates of Hell and cast in 1887, had been bought by its vendor at Christie's New York in 1999 for $4.4m. Expected to bring $9m to $12m, it took $16.9m (£8.6m).
Europeans (including significant Russian buying) accounted for 52 per cent of the buyers at Christie's. Americans made a relatively modest 32 percent of the purchases - evidence perhaps that a weak dollar and economic anxiety, that has deepened in recent months as sub prime credit losses topped $300bn, was taking its toll. However American buyers were stronger at Sotheby's the following day acquiring 67 per cent of lots.
In the wake of a difficult November sale of 76 lots that fell $85m short of its low estimate, this was more edited selection. Sotheby's 52 lots posted a hammer total of $208.6m, inside its estimated range of $203.9-280.1m. The results were, however, largely similar to those at Christie's sale. Eleven lots did not sell including a large but late Leger, estimated to fetch $12-18m and again guaranteed.
Five bidders competed for Edvard Munch's Girls on a Bridge, 1902. This is a picture with a recent saleroom history: in 1980 the painting was sold at Christie's for $2.8m. In 1996 Alan Hobart of the Pyms Gallery, bought it at Sotheby's New York for $7m on behalf of Graham Kirkham, the London collector and founder of the retail chain DFS Furniture. Sotheby's, confident of Munch's rising stock, approached their vendor in the belief this canvas from a well-known series, could fetch $24-28m. It sold at $27.5m (£14m), a record price for the artist at auction.
Giacometti was again strong - Portrait de Caroline, a 1963 painting of the artist's lover and frequent model sold to a telephone bidder for $13m (a record price for a painting by the artist) - and there were five bidders hoping to acquire Picasso's painted bird bronze La Grue fashioned from domestic objects including the blade of a shovel, two dinner forks and a gas spigot. Conceived in 1951-52 and cast in 1952-54, it was estimated at $10-15m and sold at $17.1m (£8.7m).
At this week's Contemporary sales the stakes are higher still with close to $1bn of post-War on offer including a $70m Francis Bacon triptych.
By Roland Arkell