Starting tomorrow, June 19, 2009, Apple will have three different multi-touch pocket devices on the market: the second-generation iPod touch, the iPhone 3G, and the new iPhone 3GS. Prospective iPhone 3GS customers have a choice between several alternate purchasing options—purchasing an iPhone 3G, purchasing an iPod touch, or purchasing nothing at all. Additionally, some potential iPhone 3GS customers are considering upgrades from the original iPhone, and want to quickly know what’s different between the 2007 and 2009 models. Ahead of tomorrow’s iPhone 3GS launch, we’ve assembled this quick reference guide and model summary to help make any user’s decision easier.

iLounge Model Summary:

iPod touch 2G (9/2008, iLounge Rating: B+). Apple’s best iPod touch yet, coming close to an iPhone minus phone and camera features, while offering Nike+ and graphics performance that aren’t found in the standard iPhone 3G model. An easy, smart pick to avoid AT&T contracts and still get most of the experience. Expect a new model in September 2009, quite possibly with an integrated camera, more storage + better graphics.

iPhone (6/2007, iLounge Rating: B+). Though discontinued, the original iPhone is still Apple’s best-looking model, the least expensive to operate on a monthly basis ($20 versus $30 + SMS), and capable of running virtually every app ever sold in the App Store. It lacks a variety of new but arguably minor (for now) features; its age puts it at the highest risk of being unable to run post-3.0 versions of the iPhone OS, and AppleCare extended warranties may be hard to come by.

iPhone 3G (7/2008, 6/2009, iLounge Rating: B). What Apple’s 2008 iPhone 3G dropped in initial price from its predecessor, it made up for in more expensive service contracts and less impressive body quality. It also saw battery drops in some categories, most markedly in 3G calling time, a pain point. But it also gained faster data speeds, limited GPS functionality, and markedly better audio quality through both its headphone port and speakerphone. At $99 as an initial price, your only regret in buying it today will be next year’s better sequel.

iPhone 3GS (6/2009, Not Yet Rated). The newest iPhone model offers improved storage capacity and a combination of new CPU, graphics, and RAM chips that will let applications run faster—at some point, better than on any other model, too. A video camera, much-improved still camera, Nike+, voice control, and accessibility features add to its appeal over the iPhone 3G. But 3G talk and data battery time remain potentially major show-stoppers, and as with last year’s iPhone 3G, apps that use its extra power may be far off.