Friz,
My pallet forks are one of my most-used attachments. It makes moving material around so much easier. Right now I've got paving bricks, stone, firewood, lumber, scrap, 4x8 sheets, 5 gal buckets of used hydro oil, old batteries, etc. all palletized. I even built some 42 x 42 x 36" metal cubes that I use for gang boxes with my tools and other loose items that I can stack three high if I want. I palletize all my other attachments so I can move them around easily if I need to, plus it keeps them off the ground.
I constantly use my pallet forks for brush removal. I just pile up branches or whole trees, being careful to keep them somewhat aligned, and then ease into them with the forks. 42" forks will pick up a ton of brush, and I usually leave very little brush on the ground, just using the forks. Maybe some other members may enlighten me, as I don't own a grapple, but it seems a grapple would only improve my ability to "tug" on a load, pick up a load while pitched downhill, or stabilize the load. I don't see it meaningfully adding capacity. Personally, I don't perceive a need for one, for what I do.
One thing that would concern my regarding a grapple is, in fact, having a long load so securely fastened to the FEL, especially on a hill, sideways. If your property is pretty flat, I wouldn't worry too much about it.
Consider 4WD and a box blade. I don't think 42" vs 48" forks would make too much difference.