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If the coin decides to stick with GPU algo its only a matter of time before another 51 percent attack is performed by a secret asic miner that cracked the asic resistance. Best to get it over with and stay an asic coin for better network security over gpu.
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I bolded the key phrase that invalidates your entire argument. The manufacturer of the "secret ASIC miner" is also the one most likely to be running them. In fact, selling a fraction of the ASICs you make to the public and keeping the majority for yourself is a great way to maintain control over a coin's network, bring in lots of money from mining, and pay for their development.
This can also be done by selling, say, a 10kSols/s ASIC to the public when you already have a 50kSols/s version working. You know, like seems to be the case with Bitmain's Equihash ASICs? Or sell a 20kH/s CN miner for a few weeks then roll out a 240kH/s version (like Baikal did).
Even if you don't care about principles and ethics, buying an ASIC when the manufacturers do what they have done over and over again is just shooting yourself in the foot. The fact that BTC and, eventually, LTC were taken over by ASICs without much negative consequence probably has more to do with them being the first ones; in other words, the ASIC manufacturers learned some new tricks and tactics since then.
It is a good argument. It is better not to buy ASIC.