Neither of these is really comparable with iWeb which is a, now out of dated and non supported, $15 drag and drop app.
Wordpress is more a content management system (CMS). There is a huge ampount of info about it and it is very popular. Although its capable of creating good websites in the right hands, its more suited to bloggers who want a website as well.
Muse is still in Beta and has some promising features but doesn't appear to offer much in the way of compatibility with mobile devices apart from liquid width. It looks like Adobe has invented another way to print money since you have to rent it on a monthly basis. To justify the cost you would need to be designing a lot of websites and/or making some money from them.
I am happy with I WEB,but if WP offers better custom performance and look,then ......maybe I WEB could be updated.
Giger says that WP is not that easy or better vs I WEB.
But ...like you said,I WEB has no future,but...........maybe still good.
It would be great to get a fluid software that adopts to screen browsers needs,to maximize real estate.!!!
Liquid layouts and responsive page widths are easy in that the width is expressed as a percentage. The ones I have used are locked to a maximum width to stop them spreading all over the place on computer screens...
I use a WYSIWYG code entry style software for this - Rage Web Design - $60. Cheaper, and almost as good is Taco at $25 and Fraise is free.
You need to know some basic CSS and HTML to do this but it ain't rocket science. HTML5 is - more or less - with us and it makes a lot of stuff easier to accomplish.
My main interest is audio and, to a lesser extent, video. HTML5 makes this a lot easier and elastic movies are a breeze...
With WordPress, you can use either the free version at http://wordpress.com where your site is published to the WordPress server or you can purcahse hosting and then install http://wordpress.org at your host. This needs a database, but most good hosts that offer the Content Managements Systems such as WordPress, Drupal and Joomla offer easy one click installation.
With WordPress.com, you can upgrade to use your domain name with it if you want to, but it might work out cheaper to use WordPress.org with a host. With Wordpress.org you get plugins etc to enhance your site and there are lots more things you can do.
I decided to change and have used iWeb for quite sometime for both of my websites. I needed to register a new domain name for a new business/practice and decided to go with HostExcellence where I got a free domain name. They offered WordPress so I installed it on my server and now have a new website using WordPress. I don't have a blog with it and it can be used to create a good looking website without a blog - I have embellishments using plugins for a for a Forum feature, I have online payment using the Google checkout plugin, Contact forms with Captcha etc. and it is a good functional site without a blog.
You don't need to keep and save a domain file and as long as you can get online on any Mac or PC, you can update your site from wherever you are - simply enter your domain name and then login.
The good thing about WordPress too is that you can easily allow people to register for your site and you can allow different levels of access, such as read only or read and write ability. When they register WordPress automatically generates a password that is sent to them so that they can log in and then change it. When you log in as admin, you have access to be able to alter everything and theoretically you can have pages of the site that are only available when people register and log in.
There is a lot more that you can actually do with WordPress.org, so it would be well worth exploring and you could also look at Drupal too as this is another of the CMS's.
Don't know anything about Adobe Muse.
Anything else is at an advantage to iWeb, it being deep sixed by Apple. Why learn iWeb with the knowledge that at any update it will no longer work with the operating system you might want to use. Add that to the knowledge that the free Weebly, for instance, will do most of what low-demand home users like me need.
I took a good look at Muse by watching tutorials at Lynda.com. If you had the $25 for a month's access I suggest you consider checking out her site for tutorials on Muse and Wordpress.
I came to the conclusion that if I had money to burn, I would switch to Muse, as when I got the hang of it it was fun. One will be able to spend around $50/month to get access to Adobe Creative stuff, including photoshop and premiere pro and Muse.
But, money is a problem for me, so I am sticking with Sandvox.
So many choices out there, including the free Weebly and Freeway Pro...