Both platforms bundle a small number of free camera licenses with every NAS and charge for more -- here's how to figure out the right number before you buy either the NAS or the cameras.
Neither Surveillance Station nor QVR Pro lets you add cameras for free indefinitely. Each connected camera consumes one "channel" license, a fixed number of which come bundled with the NAS itself; adding more cameras beyond that requires purchasing additional license packs from Synology or QNAP directly. This is separate from, and easy to confuse with, the camera compatibility question this site's databases answer -- a camera can be fully compatible with your NAS's Device Pack version and still need a license to actually add.
Start with your real camera count today, then add a small buffer for cameras you're likely to add within the next year or two -- a new entry point, a blind spot you noticed after the first install, a garage or shed. Buying one or two spare licenses upfront is usually cheaper and less disruptive than buying them one at a time as you expand, since license packs are typically sold in fixed bundle sizes rather than individually.
Every NAS model also has a hard maximum number of camera channels it can run at all, regardless of how many licenses you buy -- a ceiling set by the hardware, not the license pricing. A small 2-bay unit might top out well below what a larger Plus-series or dedicated NVR model can handle. If you're planning for more than a handful of cameras, check both numbers for any NAS model you're considering: how many licenses come free, and what the model's actual channel ceiling is. The NAS model database lists the bundled license count for current and legacy Synology and QNAP models; the channel ceiling is model-specific and worth confirming directly on the vendor's own current spec page before buying, since it isn't always published in the same place as the license count.
As reflected in this site's own NAS reference data, QNAP's mainstream TS-x64 line has generally shipped with more bundled free licenses out of the box than Synology's equivalent Plus-series DiskStations -- worth factoring in if license cost specifically (rather than raw hardware specs) is driving your platform choice. Synology's dedicated DVA-series NVR appliances buck that pattern in the other direction, shipping with substantially more bundled licenses than its general-purpose DiskStations, since surveillance is the whole point of that product line rather than one use case among several.
Once you know roughly how many cameras and what resolution/codec you're planning around, the bandwidth & storage calculator built into both camera databases (near the bottom of the Synology site and the QNAP site) estimates network throughput and storage footprint for that camera count, and shows which current NAS models already include enough licenses to cover it without an extra purchase. See planning NAS storage for camera recording for the reasoning behind that calculator's numbers.