In-camera wifi might be convenient, but has these disadvantages vs. a $50 dedicated gps logger:
I assume you mean in-camera GPS. Now I'll give the counterpoint for each point.
* drains camera power, you might even forget to turn it off
Requires a separate power source. You might even forget to turn it on, charge it, or replace the batteries, then find out that you have no location data for any of your pictures at the end of the day. By contrast, most people carry more than one camera battery, and believe me, if you're taking pictures, you notice when it runs down.
* much(!) less precise / updates pos. much more seldom
There's absolutely no reason why this should be the case. In fact, if anything, the reverse should be true. The camera should query the GPS for its actual position when you take a shot, and should only use a stale position if it doesn't have a valid signal. So using any sort of track log is much
less precise than proper in-camera GPS. The only situations where that is not true is when you're indoors in a location where a large GPS unit with a large antenna happens to be able to get a signal where the camera's GPS can't. But even then, you're only as accurate as the interval between samples allows, which means it might be more precise, but it might also be less precise.
* not always in the best signal position (you can put a small tagger in your breast pocket, ...)
If anything, that's a worse location. Your body soaks up signals. The farther away from that bag of meat, the better.
* camera is larger than a logger: if you want to do travel logs you always have to carry your camera around
A GPS logger is one extra device. Chances are, you're going to have your camera with you anyway. And if you really just want a log of where you're going rather than where you took specific photos, chances are, your smartphone also has GPS and can do the logging without the need for carrying yet another device.
* no wayfinder/geocaching mode (you cannot set coordinates and let the logger guide you)
Typically, the GPS receivers people use with cameras are tiny devices whose UI consists of little more than a switch to change the sampling interval, a slot to stick a flash card into, and a power switch. They don't even have a screen, so they're no more useful than the in-body GPS. But at least the in-body GPS *could* be adapted to do those things with a firmware change. An external logger without a screen can't readily be modified to do that at all.
Besides, again, you probably have a smartphone, and it can probably do all those things. The purpose for GPS in a camera is to tag photos. Anything more than that and you're probably just duplicating functionality that the user already has in a more appropriate form factor (phone).
* no a-gps (camera needs longer to find the satellites).
aGPS is certainly an interesting technology, and certainly useful, but in practice, the reason it matters in smartphones doesn't apply to GPS devices that are solely used for cameras. It's important for smartphones because the satellites transmit data very slowly. For a device to get a GPS fix, it requires a critical piece of data, the ephemeris, which tells where the satellites are in the sky. It takes half a minute to stream that data via GPS satellites. aGPS can cut this so-called "warm fix" down to a couple of seconds by fetching that data over the cellular network.
In the context of a phone, the difference is critical because nobody wants to sit there waiting for half a minute waiting for their phone to show where they are. With a camera, however, you usually switch it on at the start of the day, and GPS remains active through the day (unlike a phone, where the receiver is active only when in use). Therefore, after that first thirty seconds, the only time the camera needs to re-acquire the ephemeris data is when GPS has been shut off for more than four hours since it last received GPS data... and possibly when you switch batteries, if it doesn't persist that data across battery swaps.
Thus, unless you're very rarely taking pictures, the warm fix time affects you once per day, and only if you don't power up the camera until just before you take your first shot of the day. After that initial warm fix, every acquisition should be a "hot" fix, which means that it should take about as long as it takes you to move your thumb from the power switch and pull the camera up to your eye, give or take a second.
The one disadvantage of the gps logger that you have to attach the track log to your pictures afterwards, but this is done with one click in Lightroom or other apps. For me, in-camera gps is a gadget I could really do without.
The bigger disadvantage is that it has no idea when you actually took a picture, so you have to choose a query interval that trades battery life for accuracy or vice versa. And it's another device to forget to charge, to forget to turn on, to forget to put new batteries in, etc. Also, you have to regularly synchronize the camera's clock to the GPS receiver or you're in for a world of hurt.
In short, the external devices are a significant hassle compared with in-body GPS, with no real benefits unless you are using a full-blown GPS receiver with a screen, you want to use it for some non-geotagging purpose,
and you do not already own a smartphone or other handheld GPS device.
