I'll post an answer just to make sure people don't forget the competitive aspect (especially in singles; both are pretty useless in doubles). First, I'll paste Blaziken's BSS analysis so it's easier to see why Blaziken is so much better than Incineroar.
Blaziken is an incredibly versatile sweeper. Its access to Speed Boost allows Blaziken to easily snowball during late-game, threatening to outspeed and KO opposing Pokemon. This is made easier with its good Fire/Fighting-typing, making quick work of Pokemon such as Aegislash, Mamoswine, Ferrothorn, and Mega Mawile. Furthermore, its movepool allows it to act as a mixed attacker, capable of luring in Pokemon such as Mega Salamence or Landorus-T before KOing them with Hidden Power Ice, or being able to Baton Pass stat boosts onto one of its teammates. Finally, Blaziken has a strong Mega Evolution that allows it to outspeed key threats after one Speed Boost, such as Choice Scarf Tapu Lele.
I would be including something about Incineroar, but it's so insignificant that the guys on Smogon haven't gotten around to writing any Incineroar analyses.
Next, I'll give a few more or less objective comparisons. First, Blaziken is banned from OU, while Incineroar is untiered. In case you don't know about Smogon tiers, the first usage tier is OU. All the Pokemon deemed "unhealthy" in OU, such as Blaziken, are banned. This means that Blaziken is so overpowered that it easily beats most of the top Pokemon that aren't box art legendaries. Meanwhile, all the Pokemon that are used less than 3.4% in OU are allowed in the UU tier. This process creates a format where the top 50-60 OU Pokemon are banned, so Pokemon that are useless in OU can thrive in UU. This has so far been repeated for two more tiers, RU and NU. Incineroar is so useless that it hasn't made the 3.4% cutoff in any of the tiers, so it's currently untiered. (source) Second, in all singles formats where both Pokemon are allowed, Blaziken is consistently used more than Incineroar. Compared to Incineroar, Blaziken is about...
20 times as useful in Anything Goes
200 times as useful in BSS
88 times as useful in Ubers
Obviously, Blaziken is better than Incineroar in almost every way, at least in competitive battling.
If you're asking which one is better without evolving, then the answer would still be Torchic. Litten isn't good in any formats, while Torchic is at least good in LC. Again, here's Torchic's analysis.
Torchic has a relatively good niche as an offensive support Pokemon, since it is the only Pokemon with access to both Speed Boost and Baton Pass. Its access to some good boosting moves such as Swords Dance, Curse, and Flame Charge along with its relatively good support moves makes it an excellent Speed passer. Its offensive stats, both physically and specially, are also nothing to scoff at, as the offensive pressure it has can force a fair number of switches.
Again, Litten is so useless that Smogon hasn't yet gotten around to writing its analysis. As for the statistics, Torchic is about 85 times more useful than Litten in LC.
