Streak gets bogged down and turns into a mess as soon as you have any real volume, basically making Gmail slow and feeling like a clunky spreadsheet stuck in your inbox. It's only worth considering if you're absolutely set on running your CRM out of Google Sheets and don't care about performance.
GoHighLevel is even worse on the practical front. It doesn't just underdeliver on software quality, it ties you to a reseller's account, meaning you don't control your own data or even your subscription. If the person above you cancels or misses a payment, your whole setup can disappear. This isn't just inefficient, it's risky and unreliable.
If you're forced to pick, Streak is the lesser evil for actually getting CRM work done yourself, even if it's slow and messy. GoHighLevel's whole structure means you're never in control, which is a dealbreaker for anyone serious about running their business. Avoid both, but if you absolutely have to use one, Streak at least lets you keep your own data and doesn't lock you into someone else's payment chain.