Despite the premise being akin to a ton of oranges versus an acre of figs, there’s a new meme floating around the blogosphere that says at some point over the next three months, the combined number of iPhones and iPod touches will certainly exceed the number of PSPs.

The maths goes as such.

There are currently around 50 million PSPs in the world; at least Sony announced a 50 million cumulative total had been shipped or 'sold-in' (ie manufactured) in February 2009.

There are currently around 45 million iPhones and iPod touches in the world, so says Apple as part of its most recent Q3 financials.

In the past three months, Apple sold 5.2 million iPhones, including over a million of the new iPhone 3GSs. So by the end of September 2009, the install base of the hardware group that Apple refuses to define in discreet terms of iPhone and iPod touch is likely to be at least 50 million, plus however many million iPod touches have been sold.

Hence - goes the thinking - if, by the end of September, Apple sells more iPod touches than Sony sells PSPs, it will have overtaken it.

Of course, there are some fairly important caveats to this conclusion. Most notable is that February was rather a long time ago and presumably Sony has “shipped” more PSPs since. Probably a couple of million more at least. (And no, we’re not going to delve into the difference between a “shipped” and an “installed” PSP.)

Also we don’t know how many iPod touches Apple sells a quarter because it doesn’t tell us. All that was remarked from the most recent financials is that iPhone touch sales were up 130 percent year-on-year.

Perhaps, the most important gotcha in terms of the overtake happening during the next three months however is that on 1 October, Sony will launch its PSPgo hardware revision, which is bound to boost sales significantly.

Still, with that said, peak sales for PSP were around 6 million units per quarter. Clearly the combined sales figures of iPhone and iPod touch - hardware launched more than two years after the PSP least we forget the relative unit sales  - comfortably exceeds this, so yes, at some point, there will be more of them than of the other.

This will probably happen after October, but if PSPgo is a big success, maybe not until as late as spring 2010.

We hope everyone’s happy now. In the proper context, we like both oranges and figs.