Battery life is the big one. A compact device might last a few hours of intermittent use, but if you're training back-to-back sessions, you'll need to plan charging breaks. Some models have pass-through charging, but that's not universal.

Another thing to watch is vapor production. Smaller chambers and lower wattage mean thinner vapor. If you're used to dense clouds, a compact can disappoint. That's not necessarily a problem—it's a matter of preference.

Also, consider the mouthpiece. Some compacts have short mouthpieces that can get hot with extended use. A longer glass or ceramic tip can help, but that adds length.

Here's a concrete example: imagine you're training a new hire on product knowledge. You want to demonstrate a device's features without a huge setup. A compact unit lets you do that quickly, but if the battery dies halfway through, you lose momentum.