What They Have in Common
Both are push carts from Sun Mountain, both carry a 3-year frame / 1-year other parts warranty, and neither has a published folded size. Sun Mountain simply doesn't give buyers a folded dimension for either cart, so you can't settle the trunk question from the spec sheet alone.
Where They Differ
Wheels and weight
The PX4 runs four wheels with extendable front axles; the Speed Cart X runs three. Four against three — that's all that can be said about it from the specs. What can be said about weight: the PX4 comes in at 17.2 lbs and the Speed Cart X at 18.6 lbs, a 1.4-lb gap in the PX4's favor. That 1.4 lbs is the kind of thing you notice at the tailgate, twice a round, for however many rounds a season you walk. Whether it matters to you depends on how often you're hoisting it.
What's in the box
This is where the comparison gets lopsided. The PX4 ships with dual umbrella holders, a drink holder, an accessory console, a mesh basket, a valuables pouch, and bungee bag straps. The Speed Cart X ships with an adjustable umbrella holder and a magnetic rangefinder plate. That's it, as far as Sun Mountain's published copy goes — cup holder, storage console, and bag retention are all unpublished for the Speed Cart X, so it's not possible to say they're absent, but they're not listed either.
If you'd rather see the drink holder, basket and pouch listed than wonder about them, the PX4 removes that question before it starts.
Hardware and fold
The Speed Cart X does list one thing the PX4 doesn't: stainless-steel fasteners and bearings, plus an upgraded brake cable and upgraded wheels. Sun Mountain's copy lists those as specific improvements. The PX4's fold is described as the E-Z Latch System in two steps; the Speed Cart X has no published fold mechanism at all. No brake type is described for either cart.
Price
The Speed Cart X lists at $299.99, the PX4 at $330 — a $30.01 gap at list. The PX4 lists for more and lists more in the box; whether the box contents justify $30 is the real question on this page.
Who Should Buy Which
Buy the Sun Mountain PX4 if:
- You want everything ready to go on day one — umbrella holder, drink holder, bag retention, basket, and pouch already on the cart.
- You'd rather lift 1.4 lbs less at the tailgate.
- You want a four-wheel cart and extendable front axles specifically.
- You need to know what you're getting before you buy it; the PX4 publishes more detail.
Buy the Sun Mountain Speed Cart X if:
- You have a rangefinder and want a magnetic plate built into the cart — the PX4 doesn't list one.
- You specifically want stainless-steel fasteners and bearings.
- You're happy with a three-wheel cart and don't need anything extra in the box.
- Thirty dollars is the deciding factor and you're fine with the thinner spec sheet.
The Bottom Line
The Speed Cart X's stainless hardware and rangefinder plate are genuine features, and $299.99 is the lower list price. But Sun Mountain publishes almost nothing else about it — no fold details, no bag retention, no brake type, no cup holder status — and the PX4 is lighter, lists more in the box, and is $30 more at list. On a page this thin in published data, the cart that tells you more about itself and ships with more included is the easier choice.
Get the Sun Mountain PX4.