Tractors (like everything else) seem to break up into time and money. You will never hate that you bought a
grapple, but you also aren't going to dig out notable stumps with one. Owning both is 2X the cost. Using multiple implements on the front means you also need to be able to have access to all of them AND don't mind traveling back and forth to do so. If you are at your place that may be one thing where you can do the job in phases vs. going to a hunting property or job site and needing to haul all the stuff with you and it MUST be done in one trip.
I own a dual-lid long bottom
grapple, tree puller, and stump bucket (no
grapple). There is some overlap in function, but none perform the same task and this comes with a price. The barn is in the middle of 60 acres so I can swap out attachments easily enough and can dig stumps one weekend, come back and stack, and then move piles days or weeks apart. I normally don't have that much free time so I like to just get it done asap.
If you use the time portion to your advantage, you might be OK with the stump/
grapple combo if you stack piles and let them age so they "stick/clump" together. It may not be as efficient, but would work reasonably well at half the cost. This is one way people do it with pallet forks and no
grapple. You will drop some little stuff, but if it is small enough, you may be able to clean it up with a rotary cutter/flail which could be your rear ballast depending on how much room you need to work.
If you are digging out large stumps and root balls, it would depend as I presume both the SB/
grapple and
grapple would be doing one at a time anyway just based on weight.