TL;DR:
Smart / Programmable Splitters have wrong in-game descriptions, deceptive UI, and they provide little new utility. In a game with relatively few items / buildings etc., it is especially detrimental to the game's experience when two of these items, which are acquired mid-late game, are nearly useless.
Full Explanation:
1. Deceptive Descriptions / UI
Read the in-game description of both the splitters:
- Smart Splitter: "Splits conveyor belts in three. You can set a rule for which part should go to the left and which part should go to the right".
This is simply wrong. You can set a rule for left right but also center.
- Programmable Splitter: "Splits conveyor belts in three. You can set rules for each output to decide exactly where each part should go."
Not necessarily false, however this would be a correct description for what the Smart Splitter already does, not the Progammable Splitter. In addition to being able to "set rules for each output to decide exactly where each part should go.", you are also able to have multiple part types set for each output direction.
Next problem is with the actual interface and info provided in it when using these splitters:
- For both of them, nowhere is it specified that you can't pass the same part through two outputs. For example, consider an input belt that is 2/3 resource A and 1/3 resource B, you want to split the outputs such that 2 get A and 1 gets B. Nope can't do that. For both smart and programmable splitters, you can only send one resource type out of one output.
- Also for both, "ANY" really means ANY-OTHER, which follows the previously stated functionality in that you can't pass resource A to two outputs.
2. Only Useful for Sorting... AKA Niche / Useless
You can use these to sort a "messy" belt, which in my opinion, having mixed belts for the sake of sorting it later is bad practice anyway. Don't mix belts ;). But whatever if you like mixed belts it's your factory not mine, and maybe you've found a situation that it is more efficient to have mixed belts.
Due to the previously mentioned functionality of not being able to send the same resource out of 2 outputs, using these in a production line for attaining desired ratios of parts for assemblers etc. is nigh impossible. Furthermore, if you go through the effort of getting this to work (I have for alternate quickwire), there is never a reason to use the programmable splitter since the smart splitter will be doing the exact same thing and is cheaper to make.
3. Overall Gameplay Impact
- Very few items in game as is, and these splitter items being so niche and so late game makes them feel even less impactful.
- Ratio control on production is a major part of this game, and the two items that seem like they should assist in that completely fail to, essentially making optimization mechanics the same from the first assembler all the way to a fully fledged produce-it-all factory.
- Even if they are intentionally supposed to only be used for sorting, and some unreleased items will provide this "ratio control" functionality in the future, their in game description and UI still completely fail to convey what they are to be used for, and what their limitations are.