Why was this question closed? It is not a shopping question. Is is a question asking for input on real world experience of various Flash memory parts for use in embedded Linux systems, e.g. SLC vs MLC NAND, raw NANDFlash, uSD, SD, eMMC and their fault tolerance to abrupt power down faults. This is a big problem in the industry, there are 100s of posts on the Internet about various low cost Linux systems experiencing corruption in their Flash memory. Answers to the question will be of big help to future designers of such systems.
"Best" is subjective, and the question is really too broad. You could fill a book answering that question.
Narrow it down to your exact needs. The intention of the stack exchange network is to answer each question deeply with narrow breadth, not create guides that answer all questions in a shallow manner.
You say "A linux system" but that tells us nothing about read/write patterns, required lifetime, lifetime writes, etc. You haven't specified the processor you're interfacing to, or even the interface desired, other than a preference to move away from SD for unclear reasons. ("they seem too unreliable" is hardly a quantified statement).
I don't think there's an easy way to redeem the question. Maybe a simpler, "I'm creating an embedded linux system that is meant for routing (wifi) so writing will be rare, but when it occurs it needs to be very fast and reliable (logging), and reading will be common. Are there disadvantages to using TLC flash vs MLC flash in this scenario?"