Hi,
I see mentioned a "printer resolution" of 300....and 360PPI (Pixels Per Inch) to the printer. Both are valid, and depends on what printer you are talking about.
Epson printers typically print with a native DOT resolution of 1440/2880. But, you only get one dot of one color at one location at that resolution. It takes an "array" of dots to make up a color, and this is accomplished by a "dithering" algorithm. Even though a printer has a particular dot resolution, that is different than what resolution you want to send to it to get actual colors/graytones.
Typically, the Epson printers like even divisors of their native resolution, and 180PPI is typically the lowest you want to go for "normal" print sizes, with 360 typically showing (much) better results. Anything above 360, with little exception, is not used.
The Epson printer driver (at least when I analyzed this a few years ago) takes the data you send it, and res&les it to 360, then runs another algorithm on that data to get the dots it will use to make the colors you are asking it to. This is why sending it an even divisor of it's actual dot resolution typically yields the best results. The more you res&le the data, the more degraded it will become, and res&ling it only once (and not a second time in the driver) typically gives you better results.
BTW, this assumes you are not using the Piezography quad-tone printing driver, but the "regular" Epson driver. For Piezography, you want to send it as much resolution as you can give it, their algorithm is very good, and will use it...up to 720, and even if it is not an even divisor.
WRT the 300, that sounds like a commercial printer or screen resolution, not a typical user ink-jet printer (at least not Epson). So, the real answer is, it depends on the printer you are sending the data to, as to what the maximum acceptable size you are going to get is. Of course, what is acceptable is entirely subjective.
Typically, I judge output size by saying I'm going to send the minimum of 180 to the printer, and go from there. If I can send 360, I do it. Sometimes I ups&le or downs&le in PS to get to 360 (or 180), print and see what the results are. You really do need to experiment for what gives you the best results, as it is not only equipment dependant, but image dependant as well.
If anyone wants a further explanation of the mechanisms involved, I'm more than happy to elaborate.
Regards,
Austin