Obviously water is cheaper and cost is always dependent on how long you have played in your world. I have just a few weeks invested into a world and havent really mined in over a week, and have thousands of iron stored up, etc. 10 MFSUs hooked up to 40 magmatic engines, 20 generators for alternate power, etc. Unless you are just starting out, can the cost of 10 railguns be considered 'a lot' of resources? If you are running 4 quarries, you have a lot more resources than I do.
Railguns on MPS power gloves arent too expensive, you would need like 8 or 10 of them.
I think the key is that if you killed the blazes faster, you might need LESS spawners. You invested more time and energy into making mroe spawners, i would make railguns. Its more fun for me to make railguns and figure it out than it is to just go the regular route, but to each his own.
Having multiple spawners looks very cool too.
Also, with turtles you can combine them with brains in a jar for Xp that can be use for more than jsut enchanting (like MFR auto enchanters or XP turtles would give you) so you can then use the XP in an uncrafting table, or to combine shards etc. So im shooting for a blaze spawner using railguns for powering generators then a pigman spawner using turtles and MFR conveyors for gold and minium stones. hmm have to make sure turtles will grab minium shards, not sure.
I just built a triple T5 spawner in a 19x9 room and was looking for some better way to kill mobs. Your system sounds perfect for that! Maybe connected to a tripwire system, so that the timer only gets activated, if there are actually mobs present? Conveyors are in place already, I was setting it up yesterday with an array of turtles.
Hmm never used tripwires, hadnt thought of that.