Golly is built for serious exploration
Golly is an open-source, cross-platform application for Conway Life and many other cellular automata. The official site lists support for bounded and unbounded universes, up to 256 cell states, multiple algorithms, RLE and macrocell files, Lua and Python scripting, and a large pattern collection.
That feature list tells you what Golly is not: it is not only a beginner board. It is a working environment for experiments that would be awkward in a small web page.
HashLife changes the scale of questions
HashLife, created by Bill Gosper in 1984, stores repeated subpatterns so future evolution can be reused instead of recomputed from scratch. It is especially strong on large, repetitive patterns.
The tradeoff is important. HashLife is not always the best way to show a smooth frame-by-frame animation, and chaotic patterns can use a lot of memory. It is a tool for jumping through time when the pattern structure allows it.
A web lab and Golly should not compete
This website should help a reader understand what a glider, oscillator, methuselah, or gun is before they open a professional simulator. That is a different job from simulating huge metapatterns.
The handoff can be explicit: explain the concept in the article, run the small version in the lab, then offer RLE so advanced readers can continue in Golly.
Working takeaway
Use the web lab for explanation and quick interaction. Use Golly when the question becomes scale, scripting, custom rules, or very long time jumps.