I don't follow Windows phones at all, so I can't comment on the Lumia.

Not sure where you can get a new, unlocked S4 Mini at anything like $219, and at the prices charges as a unsubsidized carrier-locked phone (around $350) it doesn't seem very interesting -- that's a lot of extra cash for a fairly similar phone.

If you can get one where the price is comparable, it's a pretty good alternative: a good bit lighter and a little smaller... down sides are slightly lower screen resolution, slightly smaller screen, and one fewer UMTS band (1700mhz, mainly used by T-mobile in the US.)

As for speed S4 Mini is dual core, but much faster per core; Moto G is quad core, but much slower per core. The S4 Mini also has an extra half gig of RAM. I don't feel like digging up benchmarks, but I suspect the S4 Mini will be just a little faster in practice.

Engadget wasn't much impressed with it, although that reflected much higher prices when first introduced:
http://www.engadget.com/2013/07/22/s...4-mini-review/