As others have said above, Pigment based inks 'may' have the lead, but getting the mfr's spec sheets will help, as I've been out of the print industry for a long time.
Your Softwares' colour space (RGB vs. CMYK) & getting a matched profile for the printer you use will also affect quality.
E.G. RGB puts 3 Red/Green/Blue 'dots' of colour on your screen & the printer profile helps 'translate' that into the printer colour Cyan/Magenta/Yellow/Black (no white btw).
That means every 'dot' of colour on the page could be made up of up to 4 dots of varying sizes of CMYK (the Resolution).
The method used will also sometimes give a checkerboard/tartan look (most often with re-scanned magazines/papers).
The 'holy-grail' of short-run decal production was the out of production ALPS printer, which could print white, used dye-sublimation not CMYK & was eye-wateringly expensive.
A Cheap Ink-jet is just that, cheap, & the higher quality ones needed for decals would put a colour laser printer in reach, especially if you consider other uses for it. DPI is always the primary concern for quality, but you will also need to consider the cost of replacement carts as well.
A third option would be someone like Fantasy Printshop, & others.
Read carefully his requirements & tips for production, but I think 25 A5 sheets of a popular subject, shared with a hobby club wouldn't be too bad on cost, esp if you could produce white decals.
Good luck.