I'm a fan of AppGameKit Classic. I find it more intuitive and user-friendly. This is especially true for new users.
For example, AppGameKit Classic's help takes the user to webpages for each of the commands, many with code examples on how to use them. AppGameKit Studio gives you some info in a side column with no examples. AppGameKit Classic also adheres to a lot of basic standard IDE conventions that AppGameKit Studio lacks or handles in an odd manner.
- access to variables, constants, functions, etc is in the AGKC side tab one can keep open like most other IDEs, whereas AGKS has them as dropdown lists
- in AGKS, files that you have edited are tagged like other IDEs - the asterisk by the filename in the tab. AGKS marks it in the project list in the left column.
- Save All is inexplicably missing from the File menu.
- AppGameKit Studio defies its own conventions sometimes, either making for confusing syntax or creating extra work. Using the Comment Toggle is an example of that. It uses a unique set of symbols, so it only works on comments you have generated with that feature.
To be clear, I am not saying that these things are hard to learn or tedious to deal with, rather that they add to having to learn an unconventional IDE on top of learning a new language/engine. And, yeah, that crap Replace window bothers the heck out of me.