The coin needs to be the first legitimate instance of its kind, had a fair start/emission, and a market niche
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Litecoin FAIL (not the first of its kind)
Peercoin FAIL (no market niche)
Bytecoin FAIL (not fair start)
Boolberry FAIL (not the first of its kind)
Ethereum FAIL (questionable start)
All shitcoins FAIL (2-3 counts)
Only BTC and XMR fulfill all conditions, so it makes sense to invest into them (and them alone). To be fully hedged, you can keep 99.8% in BTC and set 0.2% aside in XMR. Going over this ratio, is overinvesting in XMR.
It is not hard to come with these understandings after a generous overview of the top 50 altcoins, reason why I'm as uninpressed with LTC market as with its innovative features (none).