I think you're point has significant merit but at the same time you can't waive a magic wand and eliminate speed of transaction from the real world equation.
I'm not trying to eliminate it, I am trying to say that in the dichotomy between litecoin and Bitcoin, the 4x blocktime difference is meaningless.
The remaining aspects of transaction time only serve to buttress my point - whatever coin provides true utility to more users will in time subsume the vast majority of the market.
Transactions seem to be prioritized, in part, based on what, if any fee, is associated with them. If you use BTC and your transaction had a small fee, it might take significantly longer to confirm then if you paid more or used an altcoin. To some people, this has value, look at HFT. In a similar fashion, your later point assumes that sidechains will eliminate the need for other coins which offer differing values of utility (or I thought it was your point, I can't find it anymore lol).
No. Sidechains are a distraction. If the main blockchain of some coin supports all transactional use cases, and the Bitcoin blockchain supports only 'high value' transaction use cases due to some arbitrary maxblocksize limit, over time Bitcoin will become marginalized, and the alt will subsume Bitcoin's market cap.
Your assumptions also seems to neglect the fact that people like choices. Coke/Pepsi, Visa/Mastercard/Amex/Discover. ...
I guess what i'm trying to say, is, I need help understanding why there should be only one coin. I think you can have too many coins, but just having one doesn't seem to make sense.
Coke and Pepsi both provide rehydration and a sugar boost in pretty much identical quantities. The only difference between them is a slight flavor difference. IOW, they fulfill exactly the same use cases. Invalid comparison to two coins where one fulfills the universe of use cases and the other only a proper subset.
Likewise, Visa/Mastercard/Amex/Discover have differentiated use cases. Amex doesn't give me 5% back on all purchases. Visa doesn't partially make my car payment. Mastercard doesn't get me free stays at airport lounges. Discover isn't 'everywhere you want to be'. Again, differentiated use cases -- due to an inherent capability of the card. Not one card offers a proper superset of the use cases of the others.