[inquisitor]

I don't like the term "modem" for 3G devices either as it reminds me of 1995 when my first analogue 14.4 KBit/s modem modulated bit and bytes to frequencies in the audible range. But in fact all our fully digital communication technologies - no matter if wired or wireless - still use modulation and demodulation. E.g. the modulation schemes used for UMTS are QPSK and QAM. Even when converting electro-magnetic carrier waves into light for transmisstion through fiber-optic cables people correctly speak of "modulation" and "demodulation".

Regarding the points you made on 3G hotspots you should know that those Huawei modems, which I've recommended do not only work wirelessly, but can also be attached to a computer by USB. Then they will be detected as a generic USB ethernet adaptor and will let you access the web without requiring any additional drivers or software. And if you install and launch Huawei's dashboard (Mobile Partner) they will enter in an alternative USB mode, where they will behave like any other Huawei 3G modem, so you can enter USSD requests etc. So these Huawei 3G hotspots can be used like any of their 3G sticks if desired. Anyway I never saw the 2.4 GHz spectrum being so congested that I would experience any issue with the Wifi connection to my hotspot. That can happen if there's a greater distance between access point and client, but it's very unlikely to happen if Wifi clients are in the same or neighbouring room.
Huawei's 3G hotspots get their power supply over a standard USB jack - so you can operate and charge them also on your computer. So again no difference to a data stick.
You're right that data sticks are cheaper, but they are not as flexible and cannot be situated freely to get a better 3G signal and you cannot use the same data plan on your smartphone and laptop simutaneously as you can do with a 3G hotspot, which at some point may again cost you money if you need data on both (or even more) devices concurrently.
As of reliability of wireless technologies I've never had issues when connecting a WiFi device to my 3G hotspot - the least reliable thing here are the 3G networks, which sometimes get congested and suffer from an effect called cell-breathing, where signal gets weaker upon high load which may even push you out of the serving 3G cell's coverage.