One of the intellectual fathers of Bit coin, Luke Jr, sees that blocks are full of mostly spam, they could be cut in half (0.5MB) to better serve the purpose of uncensorable monies. Poors and spammers may use doge.
The only problem is this decission comes from artifical block size limit which is centralized regulation decision about the max block size. If this value comes from free market, ie no miner wanting to create block sizes over 0.5MB (or whatever size), then this would be fine.
"Longest" doesn't mean anything on its own. The only thing that matters is the "longest valid chain." Validity is determined by consensus rules. Even if there is no consensus on a block size limit, that doesn't stop anyone from rejecting blocks on that basis. If one miner accepts that block and builds on it, and another miner rejects it, "longest" chain loses any meaning. The latter miner will never accept the longer invalid chain.
There is not consensus on block size limit today. With Bitcoin Unlimited many people would accept over 1 MB blocks even today. The only reason miners dont mine over 1 MB blocks today is because they act rationally, most nodes (thus Bitcoin services) would reject such block and the chance to keep longest chain with mined over 1 MB block is zero today.
BTW Bitcoin Unlimited is very underestimated client, with good features and development. Definitively worth considering when your undecided whether run Core or Classic.