Any deck that runs a bunch of little creatures can benefit from having this Elf Wizard around. The first ability for 3G (3 colorless, 1 Green) puts a 1/1 green Saproling creature token into play. This is a mediocre, but usable mana-sink in Commander for sure. It’s sub-par for Constructed purposes, though. The second ability for 3W (3 colorless, 1 White) gives all creatures you control +1/+1 until end of turn. This is the stronger of the two abilities by far.
In a deck that can swarm the field with creatures, this is a fine addition. It’s not a fantastic card by today’s Constructed standards. But it still has a home in anything that runs a ton of tokens, especially ones based around producing lots of Saprolings.
The first ability for 4GW (4 colorless, 1 Green, 1 White) simply puts a 3/3 green Centaur creature token onto the battlefield. That’s very pricey token generation. The second ability for 2GW (2 colorless, Green, White) allows you to Populate, or put a token onto the battlefield that’s a copy of another creature token you control. That ability is slightly better, and with Voice of Resurgence running around as of Dragon’s Maze, the Populate mechanic can be quite relevant.
It’s a tough call here between these two, that each have their place in Commander decks, but Selesnya Guildmage is a bit better simply for being able to pump creatures for a turn. Neither is highly Constructed playable, but Selesyna Guildmage wins by a bit here. Despite the Populate ability with the Vitu-Ghazi Guildmage, the original Ravnica guildmage is just a tad more versatile.
Winner: Selesnya Guildmage, by a bit