I just started with VTTs. Played once very briefly as a player and ran a test session as a DM. My brief impressions, I play only 5E DnD.
Roll20:
This one I actually played in (both as player and GM). I basically see this as a blank battlemat. You can draw on it both as a GM and a player on a top layer. The GM can change the bottom layers, for example if you want to have a background other that white or have a predrawn map.
I think I works quite well for simple (combat) maps that you make quickly. The fact that players can draw on it helps a lot for AOE spell/effects that linger. I haven't figured out how to properly import premade battlemats. For my test session I though I could use a digital map from DnDbeyond easily. That did not work, I couldn't align the grid of the digital mat with the grid of Roll20. So I had to draw it by hand, which was kind of a pain in the ass. You can use fog of war to reveal parts of the map.
For dice rolls, you can automate a lot of it. It takes work to set it up though. You have to make a Character in the Journal page, then fill in the character sheet. For DnD it has a character builder that works well. It automatically calculates your bonuses based on stats + profiency. Once filled in, you can click on a skill/attack/etc and Roll20 makes the appropriate roll. Just You can also create 'character' for enemies. If those monsters are from the SRD, you can drag and drow the monsters stats from the ingame compendium.
Once you made a Character entry, you can also couple it to a token on the mat. This way a player can only move his own token. If you don't couple a Character to a token, you need to find the token each time you switch to a new map. You can also give the token the values of important attributes, such as HP.
Conclusion: See this as a battlemat. It's simple, nothing fancy. The fact that players can draw on it is great for the tactical combat aspect of DnD. I haven't been able to get fancy maps to work properly. You can automate a lot of stuff when you set up the characters (dont do this ingame). Monsters from the SRD are easier, you can drag and drop. Also lightweight.
Astral:
I have only tested this myself, not used it in an actual session. There is a lot of good stuff here.
It has a great map making tool. There are a lot of presets with similar style that you can drag and drop to make a nice looking map. For example you click on the desert preset and it gives you a sand background, cacti, oasis. You can than drag/drop whatever you want and change whatever you want to have in the front (think photoshop layers). Artstyle looks nice and is consistent.
Tokens look a lot better than Roll20. Each token automatically has an action bar with short cuts to different rolls (which you can customise). It automatically shows HP. I haven't tried changing the stats, so I dont know how well it works.
It has dynamic lighting that looks neat (paid feature in Roll20. Haven't used it in a selfmade map). You can also change time of day and weather effects. It also has some 3D effects. However it did not run smoothly on my end with those effects on (10 y old gaming PC).
My major criticism: You can't easily draw on the map and only the GM can change anything. I have no idea how to visualise linger AOE effects properly. Since I playing like those in DnD, I won't be using Astral.
Conclusion: If you want a map to visualise the situation, definitely consider using Astral. Nice visuals. Great mapmaking tool that is easier to use than Roll20s imo. Neat effects built into it. The automated game features look good. Performance was iffy on my end. If you are like me and like to use gridbased spell effects, I dont recommend it sadly.
In general:
Using the simple ingame dice rollers can slow the game down. I feel like having them roll in person and give me the result is faster (unless they are bad at arithmetic). The one click rollers are also quick, but have to be setup.
How is Avrae? I own all content on D&D Beyond which is why I'm not really interested in Roll20 as I do not want to rebuy content. I do want to use maps somehow but I have no experience with Roll20.
There's
Beyond20. I haven't used it, but it can send your DnD Beyond characters info to the Roll20 dice roller. Making a roll should be as simple a clicking on the relevant skill/attack in DnDbeyond and it works with monsters.
