Altcoin pump really hard during bullruns. There are much more profitable than bitcoin one can easily make alot and vice-versa .one should also be careful in choosing the best altcoins to invest in and also never invest what you cannot afford to lose cause the crypto-market is very much volatile.
You are right that altcoins always pump hard and late in a bull run. Investing in Bitcoin is considered safe, but the rate of return on Bitcoin is lower than Altcoin.If one chooses good and strong market coins to invest in, which have the potential to give a good profit in the future, then surely good profit can be earned. your suggestion is very good that crypto currency market is a fluctuating market, invest here the money that you lose will not affect your daily matters. Always diversify your capital among different altcoins. Investing in a single altcoin increases the risk of loss.
honestly though you could simply just invest in both, why? because usually they don't really increase or having a rally in unified manners.
bitcoin usually have the first bullrun and after it stabilises at its peak then altcoin will have the chance to shine, and it just means that you could be investing in bitcoin first
and then invest in altcoin which eventually you will convert back to bitcoin which gonna be a quite good strategy from my opinions.
but then again such pattern isn't necessarily guaranteed to be the same for all I know there is some cases when bitcoin and altcoin have rally at the same time.