Pigment-based inks are supposed to be more fade resistant than dye-based inks. However, they can have drawbacks. I used to have an Epson Stylus Photo 2100 printer, which used pigment inks. I was delighted with the image quality, but not so delighted when I found out that it wouldn't print well on semi-gloss stock, and not at all on gloss. Prints only looked really good on matte stock, but Epson's advertising blurb coyly omitted that fact. Make sure that the printer will print on all the paper types that you intend to use, including third-party papers. I have given up on pigment-based inks for that reason.
Ask to see sample prints for all different types of print stock and check for bronzing, especially with black ink.
The Epson 1500W is designed for dye-based inks. I would be very wary of putting pigment-based inks through it. They may clog the print head. In fact, I would be very wary of using third-party pigment inks at all, since they can be extremely substandard. I did this with my Epson 2100 and the yellow channel clogged immediately. The printer is now sitting, useless, in my garage.
Pigment inks are very difficult to manufacture. The particle sizes have to be small enough to pass through a printhead without clogging it. Unfortunately, as the particle sizes are made smaller, the ink becomes less intense (and more transparent). Pigments need to be extremely brilliant to overcome this effect and third-party manufacturers may be tempted to not grind substandard pigments finely enough to pass through printheads reliably.
Good quality pigment inks with extremely fine particle sizes will appear to be almost transparent when viewed in a transparent container. If they appear to be opaque, don't use them. If they come in opaque containers, decant them before using them. I ignored the fact that my third-party yellow ink was not transparent and immediately had cause to regret it. Caveat Lector.
P.S. Pigment-based inks used to have a smaller colour gamut than dye-based inks, but with modern ink technology, that may no longer be the case. In the end, it's a trade-off between permanence and other desirable qualities.