Two trees, planted the same decades, grinding two different ways
Silver maple and water oak both went into Madison yards heavily during the postwar building years, often within a few houses of each other on the same street, and both are now old enough that we're grinding stumps from either species on a regular basis. Despite showing up in the same neighborhoods at the same time, they don't behave the same way once a grinder's actually working through them, and the difference matters more to pricing than most homeowners expect walking up to a stump that just looks like 'a big tree, gone.'
Neither species was a bad choice for the era - both grew fast enough to shade a new brick ranch within a reasonable stretch of years, which was the whole point for a builder trying to make a subdivision look established quickly. Nobody planting a yard in 1958 was thinking about what either tree's root system would be doing to a driveway seventy years later.
Silver maple: soft wood, wide shallow roots
Silver maple grinds relatively fast per inch of diameter since the wood itself is soft and fibrous, but the tradeoff shows up in root spread rather than wood density. A mature silver maple's roots run wide and shallow, frequently reaching out further than the trunk's own diameter measurement would lead you to expect, especially toward a driveway or slab where something firm gave the roots a surface to follow. That wider root flare means more material to clear even though each individual pass through the wood goes quickly, which tends to land these stumps in the middle to upper end of their size band.
That combination is also why silver maple stumps near a driveway or a slab tend to surprise first-time callers the most - the tree looked ordinary from the yard, but the roots underneath had been quietly working against the concrete for decades. It's also why we ask about nearby hardscape specifically when someone mentions a silver maple, more than we would for most other species.
Water oak: denser wood, a tighter root ball
Water oak is a denser hardwood than silver maple at the same diameter, which means the wheel has to work harder per inch of wood removed and the job simply takes longer pound for pound. Where it can even out somewhat is the root system - water oak generally holds a tighter, less sprawling root ball than silver maple does, so while the wood itself is slower going, we're not chasing roots as far out from the trunk in most cases. The two factors partially offset each other, which is why a water oak and a silver maple of similar diameter often land in a similar price range despite grinding very differently under the machine.
Water oak's tighter root habit also means less surprise once we're actually grinding - what you see reaching out from the trunk above ground tends to match what's underneath more closely than a silver maple of the same size ever does.
What actually decides your number either way
Species matters, but access and root spread toward hardscape usually matter more within either species. A silver maple stump in open ground with nothing nearby to grind around can come in lower than a water oak squeezed against a driveway edge with roots grown into the base, even though the maple sounds like the 'harder' tree by reputation alone. When you call, mention the species if you know it and describe what's immediately around the stump - that combination gets us closer to an accurate number than diameter or species alone ever would.
It's the reason a quote over the phone always comes with a caveat - we'll give you a real number based on what you describe, but we reserve the right to adjust it honestly once the grinder's actually in the ground and telling us something different. Most Madison homeowners appreciate hearing that upfront rather than being surprised by a revised number partway through the job.
The short version
Silver maple grinds fast but spreads roots wide and shallow, while water oak is denser wood with a tighter root system - the two tend to average out to similar pricing at the same diameter. Access and nearby hardscape usually swing the final number more than species does.