For the first time in this generation of gaming consoles, Microsoft has the most expensive system on the market (the Xbox 360 Elite, which currently sells for $399). This came about when Sony announced the PS3 "Slim" for $299, and dropped the price of its current systems by $100.
How long will this situation stand? Not very, from all indications. Expect to see a re-shuffling on the Xbox 360 product line very soon now. Rather than a straight price cut, Microsoft will be phasing out the mid-tier, Xbox 360 Pro model (currently selling at $299) and drop the price of the Elite model to the current price of the Pro (and the PS3). This all is rumor at this point, but the evidence (in the form of ad scans from Meijer and Walmart showing the price cut and photos showing a 360 box that mentions only the Arcade and Elite models) is pretty solid.
Want more evidence the Xbox 360 Pro is going away (or just want a good deal?): Woot Sellout has the Pro model for $230 as of this morning (though I wouldn't expect supplies to last very long).
Exactly when does this new pricing becomes official? Most speculation says Real Soon Now. It could be Microsoft will announce the news at the Penny Arcade Expo, which starts on September 4th, but other sources say even sooner than that, with the new price going into effect on September 1st. Either way, if you're in the market for a 360 (and miss the Woot deal), hold off for a few weeks.
So with price parity between the 360 and the PS3, which is the system to choose? That's a big topic, but to my mind it boils down to what you're looking for. The PS3 has a smaller games library, but it plays Blu-ray disks, has a web browser for watching streaming video (but sadly, not Hulu, which blocks the PS3), has wireless connectivity built in, and offers free online play. It offers a more complete 'out of the box' experience. The Xbox has a much larger games library and lets you stream Netflix Watch Now, but charges an annual fee for online play (and you'll need to but an add-on adapter if you want to connect it wirelessly). Historically the Xbox 360 has had some serious reliability problems but those seem to now be behind us. If you're a social gamer looking to play online with friends, the smartest thing to do is get whichever console your friends have (and that is probably a 360). If gaming is more of a solitary pursuit for you, the choice is less clear; the PS3 library is quickly catching up to the 360's, and the PS3 has some truly unique offerings. Do avoid the Xbox Arcade model, however. That one has no hard drive, and you're going to want that storage space for downloading demos and Xbox Live games.