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. 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 Selesnya 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