I have played both to the mid 80s. This year, from level 1.
Mage is a fine soloer as long as you manage your pulls. "Gate" is your only really get out of jail card (no root, no snare, no evac, no FD) so when it goes badly, it goes badly quickly. Yes, you can bring out a fresh pet quickly (spells or AA), but it's starting from zero Hate so in general I still get pancaked.
Molo the Mage is really good.. heal my super tank pet. But when it goes badly, see above.. and I find myself at Bind. But summoning mobs are no problem, pet holds aggro.
The Wizard can root and snare, solo kiting is very productive. And you have personal (and group) escape spells and AA. Mind you I still manage to get killed, but that is not from lack of options. And the Wizard does a ton more DPS (or at least feels like it).
Even with the recent pet nerfs, I think molo Mage is very seductive. My main problem was runners.. no snare. Which is why I started the Wizard (really to just be a snare and one button DPS). What works for me is I leave the Wizard mounted and parked to regen mana and use the Mage to pull and then blast it to bits.
But then I started having mana issues.. and a Bard is really easy to park on /follow with /melody.. and can be used to pull. Which is how I found myself full time three boxing. Which is fun, but sometimes I don't want the hassle of managing it.
Mage with or without a Healer Merc is super easy to play and versatile.. unless the mobs run at low health or you over pull.
Wizard is awesome solo as long as you have room and it doesn't summon.
If I had to pick one to solo.. Mage wins. I played a Necro main for years and I'm tired of running in circles.. pet tanking with or without a Healer merc is more relaxing.
If I had to pick one to bring to a group.. Wizard wins out by a hair. No pet management, ports, and big numbers are fun.