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fiberglass batts and blown-in cellulose are the most practical options for most attics because they're affordable and offer decent r-values per dollar. fiberglass runs about r-3.2 to r-3.8 per inch while cellulose hits around r-3.6 per inch, so you're looking at similar performance. the main difference is that blown-in cellulose fills gaps better and settles over time, whereas batts need careful installation to avoid thermal bridging. if you want better performance upfront, spray foam gives you r-6 to r-7 per inch but costs way more - maybe 2-3x the price of batts.
Are you dealing with moisture issues or just straight insulation? If your attic tends to get damp, I'd lean toward closed-cell spray foam instead of the usual suspects - yeah, it costs more upfront, but it actually seals air leaks and handles humidity way better than batts or loose fill ever will. I learned that the hard way after my own attic started showing moisture problems in spring; spray foam solved it where other materials would've just trapped moisture between layers.
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