What are the (technical) pros and cons of Flash vs

Question

We provide a web application with a frontend completely developed in Adobe Flash. When we chose Flash 6 years ago, we did so for its large number of features for user interaction, like dragging stuff, opening and closing menus, tree navigation elements, popup dialogs etc.

Today it's obvious that AJAX/JS offers roughly the same possibilities and because of the number of frameworks that are readily available, it's very feasible to implement them.

Is there a technical reason one should choose either technology over the other? By "technical", I mean performance, security, portability/compatibility and the like. I don't mean aspects such as the very non-programmer way development is done in Flash or whether it makes sense to switch an app from one to the other.

As I just explained in another question, it seems to me that JS is way ahead in terms of market share and I'm wondering whether we are missing some important point if we stick to Flash.

Answer 1

JS and Flash both have great presence on the web with overlapping capabilities. One area JS is still lacking is in rendering video.

Answer 2

As I can't accept two answers, I'm going to merge Christ Upchurch's and 17 of 26's answers in my own post. I think, these two together pretty much sum up what I wanted to know. Thanks guys!

Answer 3

Although flash is pretty ubiquitous on desktop browsers, mobile support is very limited (flash lite? yeah, right). I get really frustrated looking up a restaurant on my phone only to find the entire site is flash based and I can't even get a phone number or address!

Answer 4

I suspect one of the reasons javascript is becoming more popular is that it's more easy to retrofit into an existing application.

Answer 5

If you're dealing a lot with polygons, then Flash is still easier to program and debug. With AJAX there are a lot of libraries to handle polygons, but the more libraries your app uses, the slower it gets.

Answer 6

• Correctly designed AJAX apps are more googleable than Flash
• Correctly designed AJAX apps are more easily deep linkable than Flash
• AJAX doesn't require a plugin (Flash is pretty ubiquitous, so it's not really a big deal)*
• AJAX isn't controlled by a single company the way Flash is

Edited to add: * Except for the iPhone, as Abdu points out.