Microsoft's recently announced console is narrowly edging out Sony's device, with the Xbox One securing 2.3% more pre-orders than the PS4.
The consoles are currently top of Amazon's PC and Gaming chart, despite the lack of release dates and pricing information.
"It's not clear yet which of the two will have the edge when they launch later this year," Amazon's Xavier Garambois explained.
"What's certain, though, is that fans are already excited about how the next generation of consoles will change the world of gaming and home entertainment," he added.
Meanwhile, Ketu Patel, head of video games at Amazon, said: "Both the Xbox One and PlayStation 4 are set to have a huge impact, not just in terms of cutting edge games but also as part of the way in which families enjoy home entertainment.
"It will be fascinating to see how the battle between the two console giants develops over the coming months - the fight for who's going to be the must-have Christmas present is only just beginning."
Sony and Microsoft will hold conferences at the E3 gaming expo later today.
Microsoft's conference will kick off at 5.30pm UK time, while Sony will host its presentation at 2am UK time.
Microsoft has been tipped to showcase 20 titles, including new Halo and Fable sequels, as well as a surprise announcement.
Sony, meanwhile, is tipped to unveil its PS4 hardware, and will reportedly demonstrate 40 games over the course of the week.
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