Though I haven't had the opportunity to assess the current state of the game (1.4.3), I can give my overall opinion from my "complete experience" in 1.4.2+; seeing as how Mage and Summoner were the two Classes I experimented with about an equal amount. 
Summoner is just an objectively better version of itself (from 1.3.5), but a bit confusing in it's progression tree, so I'll start with Mage first.
: The progression tree for the Mage Class has gotten a LOT more interesting in 1.4+, as it's become a 'mirror' to Summoner Class, in certain aspects, in that it encourages a method of play outside of 'direct combat'. For example, you can focus on Homestead Building activities and simply 'buy' your first set of Mage Gear from the Traveling Merchant, seeing as how there's an Economy with NPCs, allowing you to collect Gold much faster.
In addition, the Gems typically used to craft a Mage's first functional Robes & Staff/ Rod, has been made 'farmable', which means you can passively collect the ingredients needed for your first set of Gear and Magic Rod, while also doing other money-making tasks. For those a bit more "adventurous", you can go directly for the Thunder Zapper instead, which is risky, but certainly worth it! The benefit of going for this Weapon, is that you're likely to come across other specialized loot, such as Bast Statue, Magic Conch & Snake Charmer's Flute.
Edit: Almost forgot about the Wand of Sparking, which is actually a great Starter Weapon now!
Next, which is likely the most surprising addition, is that it's possible to play a certain type of Mage. The three playstyles I've come across are Aggressive (Nuke Mage), Passive (DPS+Adds/ Minions or both) & 1.3.5-ish similar, simply being a version of Ranger, but with a Mana Bar. You can start very early, too, with the inclusion of Movement Accessories generally benefiting all Classes equally. Meteorite Set is still a good progression piece, but it's not essential anymore, and you can get away with skipping it completely.
Lastly, with all of the additions and balance changes to already-existing-Weaponry, this trend continues, but with different flavors or extremes to these several playstyles. I'm not sure if the "Don't Starve x Crossover" added anything else beyond this (i.e. Bone Helm for example), so this is about where my insight begins and ends.
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[updated - 02/18/2022] The progression for Summoner Class is a weird bag, but I believe it has likely the easiest pre-Hardmode path in the entire game! The only issue one might have with Summoner Class, is being a new, unknowing player, in which the progression tree doesn't really make any sense; however, if you know where to look for the next upgrade, you can pretty much plow through most Bosses with relative ease.
Side Note: The Bewitching Table and Sentries are getting a buff in 1.4.4, so only expect Summoner's power to increase greatly.
Summoner Class is a bit more slow-paced then others, so you've gotta be a bit more patient than usual, as most of Summoner's tools are intentional and rely on rare Enemies, specific Enemies, Fishing or other RNG Mechanics. It's normally in your best interest to dart toward whatever the newest objective is, relative to the spike in difficulty, for example: darting toward the Ocean Biome during a Blood Moon Event, or darting toward the nearest Spider Cave at the start of Hardmode.
As long as you've been staying on-top of your pre-Hardmode 'business', progression for Summoner Class should be pretty easy pickings, "just don't get hit!" 
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: I think comparing the two Classes in 1.4+ is likely similar to comparing Granny Apples & Fuji Apples, they're both certainly apples, but how they arrive to the marketplace will look very different from one another. If you were to ask me which was the superior Class in Terraria, I'd honestly have them at about the same tier.
I think playing with Mage Class is a bit more fun, because Magic Spells and Mana Management have always been extremely wacky, and acquiring the Meteorite Set is still one of the biggest highlights in the game, even after 9+ years, LoL! Finally, the full Dark Artist Set is hands-down one of the sleekest sets in the entire game, it gets a 10/10 on style-points alone, but also happens to be stupid-powerful!
