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(My general approach for BTC is to just buy a few and hold them. If BTC goes global, I'll be happy, if not, and BTC becomes obsolete, no big loss.)
So, let's suppose I chose Electrum, which seems to be one of the easier ones to use.
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if you just want to hold large amount of btc i think Electrum as you said is the best choice for you. but remember to use it offline and also write down your seed on a piece of paper and save it a safe location.
i liked this post on how to create an offline electrum wallet:
https://bitcointalk.org/index.php?topic=853288.0;all