Biotech Values

[xavierprivas]

If I have 100 shares of stock A bought at $10 ($1000), then if I sell
it a year later at $20 I have to pay long term capital gain at 20%
which means I have only $1600 (100 sh * $20 = $2000 - $400 tax) to
buy stock B.

All depends on how much stock A goes up vs stock B. If stock B goes
up a lot more than stock A then you make more money by selling A to
buy B, if B only goes up slightly more than A then it might be
better to keep stock A.

This only comes up with taxable account, not 401k or IRA of any kind.