I've got a simple Cateye wireless I use on my MTB. Some of the trails we ride branch off to others and aren't marked very well. We can tell how far we've gone and get an idea of where we are, need to be or where we should have turned.

I use both a smartphone app and a computer (wired even!). I've never noticed the wires getting in the way of anything, but I'm not the most aggressive rider so take anything I say with a grain of salt. I usually just use the computer for distance and the time of day. I often have other engagements after riding, so I have a limited amount of time I can spend out there. I want to make sure my wife isn't upset when I get home.

I use a Garmin Forerunner 305 for everything (Road, MTB. Running, Kayak) and love it. They are out of production now, but you can still buy some new and used ones online cheap. It has a GPS and Heart Rate w/chest strap. I have been using them on my wrist for years and they always work. Great product for the money.

I use a pretty simple Sigma Sport wired computer on both my road and mountain bikes. They are a 90's era computer and I still can get them new off ebay for $15 or so.

I no longer ride by the numbers, but it is nice to check on mileage, especially for those times when I have only gone a few miles and have no motivation. It kinda gets my butt into gear. And yes I've crashed and have not lost it.

John

Like all members have said, for me Garmin products is a good choice, maybe you won't find the display nice, but the GPS is efficient, the battery life is Ok and this will improve your performance.

i run a garmin edge 800 gps on my road bike and like to know how far ive ridden, though on the mtb i find it a distraction and a constant worry that it will be a scratch magnet. ive taken to placing it inside a travel soap dish and carrying it in my hydration/gear pack. since it dont need wheel sensors to give a reading and has very strong satilite connection it remains accurate though not as much as having the wheel sensors.