Brushless is faster, cooler and nearly maintenance-free; brushed is cheaper and smoother at a crawl. Speeds, combo prices, kV, crawlers and the ESC you need.
Brushless is faster, runs cooler, lasts longer and needs almost no maintenance. Brushed is cheaper, simpler and smoother at a crawl. For a basher or a race car, go brushless when you can afford it. For a slow scale crawler or a kid's first truck, brushed is still a good choice and you don't need to apologize for it. Whichever you pick, the motor and the ESC change together: a brushed ESC can't drive a brushless motor.
A brushed motor switches its own current. Carbon brushes rub on a copper commutator as the armature spins, and that contact is what wears: the brushes shorten, the comm gets dirty and grooved, and over months the motor loses punch and runs hotter.
A brushless motor has no brushes. The ESC does the switching electronically, firing the three phases in sequence. Nothing rubs except the bearings, so there's far less heat and much more of the battery ends up as wheel speed. You can tell them apart at a glance: brushed has two motor wires, brushless has three (plus a small sensor cable if it's sensored).
No. A brushed ESC only varies the voltage on two wires; the motor's brushes do the switching. A brushless motor needs the ESC to fire its three phases in order, and a brushed ESC has no way to do that. Upgrading means buying a brushless motor and a brushless ESC, which is why they are sold as combos.
The ESC also sets your battery limit. Check its cell rating before you plug in a bigger pack: many stock brushed ESCs are rated for 2S LiPo or 6 to 7 cell NiMH and nothing more. If you are still choosing a battery, NiMH vs LiPo for your first RC battery covers what each one needs.
On the same truck and battery, roughly 50 to 100 percent faster. A stock 12T brushed Slash or Stampede does around 25 to 30 mph on 2S. The brushless VXL versions of the same trucks do 45 to 60+ mph depending on battery and gearing. You also get more minutes per pack, because less energy goes into heat.
The bigger change is how it feels. Brushless hits hard from a standstill, which is great in a big yard and a handful in a small one.
A brushless system outlives several brushed motors, so the gap narrows after a couple of seasons, but you still pay more up front. The cheap Hobbywing combos are good. You don't need Castle for a backyard truck.
Cheap or kids' trucks. When the motor is a $20 part and the truck ends up in a pond, a $150 combo is the wrong place to spend.
Spec racing classes. Most "stock" classes today are brushless too, but with a fixed motor: 17.5T and 13.5T are common, often with the ESC locked in zero-timing "blinky" mode. A few clubs still run brushed classes. Check the rules with your track before you buy; you can find clubs near you on Places.
Crawling is the one place brushed still wins on feel. At walking pace a brushed motor is smooth and predictable, and with a drag brake it holds the truck on a steep descent. Crawler drivers run 35T, 45T or 55T brushed motors (higher turns means slower and torquier), and many never change.
Cheap sensorless brushless is the wrong upgrade here: with no rotor position to work from, it cogs and stutters as it pulls away from a stop. If you want brushless in a crawler, buy a sensored system made for crawling. The Hobbywing QuicRun Fusion SE, for example, puts a sensored 1200kV motor and its ESC in one 540-size can, with an adjustable drag brake for holding on hills. A sensored crawler system gives you more runtime per pack and more wheel speed for trail driving without losing control at a crawl.
kV or turns. Bashing motors are rated in kV, racing motors in turns. kV is rpm per volt with no load. Turns run the other way: fewer turns means more rpm, so a 13.5T is faster than a 17.5T. More kV means more rpm and more heat. Fewer kV means more torque per amp and cooler running. As a starting point, a 1/10 truck on 2S–3S runs roughly 3,000–3,500kV. On 4S–6S in a 1/8 you drop to about 1,800–2,200kV, because the extra voltage supplies the rpm. The biggest kV number on a high cell count is how motors get cooked.
Sensored or sensorless. A sensored motor tells the ESC where the rotor is through a small extra cable, so it's smooth from zero, which is what racers and crawlers want. Sensorless is cheaper and fine for bashing, where you're rarely creeping. For a first brushless basher, buy sensorless.
Buy a matched combo. Motor and ESC from one maker (Hobbywing, Castle, Spektrum Firma, Traxxas VXL) are set up to work together. Check the ESC's cell rating and continuous amp rating, and leave headroom. A 60A ESC in a heavy 1/8 truck on 4S will overheat.
Yes. Most people drop a few pinion teeth when they convert, then check motor temperature after a full pack and adjust. The right motor on the wrong pinion still runs hot. How to do that is in pinion and spur gearing explained.
Used combos are a good buy because brushless motors don't wear out much. Check the listings for one pulled from someone's upgrade, and the deals page for new combos on sale, before paying retail.