As the web technology has matured the systems for displaying code has really improved; the browsers have had major upgrades to their screen rendering ability through the development of new "classes" of content and better ways of presenting information for search engines and computers generally has been a direct result.
The original HTML code we battled with back in the nineties was so basic that centering a photo or graphic was even a challenge. Text drifted from screen edge to screen edge - white space was minimal!
"Excuse me Sir, Your Table is Waiting!"
Again some terrible memories arise when I think of the time we spent placing web page elements into tables so that we could control the relative position of items on a page. Before WYSIWYG - "What You See Is What You Get" web authoring software, we punched every piece of code in a word processor application like "Notepad" - then loaded the page into a browser to see how it was all looking! You could spend hours finding just one offending character that was stopping the page from rendering onto the screen!
The "table" really allowed graphic design to actually become a consideration in regard to web development. The idea of the table was to define a container and then place page elements like text or graphics within that container. As a concept we could also define areas within that contained area and get some resemblance of control as to how the page would look. Control of white space between items, where they lined up etc.. was the first step to controlled web design!
But it was oh so slow and so easy to make mistakes with. Dreamweaver really was the first major player to bridge the gap and provide - so called "cross platform" design software that had some resemblance of WYSIWYG layout capabilities.
Hand Coding
The hours and years spent hand coding allows us to be very fast at fixing code today as we are very used to working at the base level of this web technology. Most of the ancient WYSIWYG programs like "Front Page"- I actually shuddered as I remembered this part of a web prelife; built web sites using layers of pages and items and graphics that gave HUGE outrageous page sizes. The complexity of the Windows excuse for web development was so bulky and bloated that it really was a terrible time for the industry. It has subsided these days and we see very few references to this style of web technology (thank goodness!)
CSS is Your "Style" and XHTML is Your "Content"
Todays web pages are so much faster if they are designed with CSS and XHTML. In its purest form CSS describes how the items on a page are rendered to screen and XHTML describes the content. So when a browser hits a web site it loads the CSS description of the site's assets and how to render them into memory and then deals with the XHTML which is the real site content of each page as it is required. Very slick and oh so fast; however there is a barrier to using the technology as CSS has its own little issues, as different browsers like Explorer or Firefox on different platforms - UNIX, Windows & Mac for example, render the result differently EVEN now that we are well into what is described by the experts as Web 2.0 standards! Separating CSS "style" and XHTML "content" also allows the search engine's far faster and easier access to the actual web site content itself; also of major consideration in any web project.
We've Come a Long Way!
We have certainly seen some great progression. To answer the initial question in the heading, small fast code under the CSS/XHTML context means that pages render faster, search engines find the content that they desire more easily, in fact the whole technology hums beautifully!
However, this style of site has one large barrier that being experience and skills. Few code generating programs actually provide clean CSS/XHTML results. So many web "designers" (a loose term) still are busy building bloated "table based" web sites, as this is the extent of their ability quite often. The difference can be as much as 70% larger code that of course slows the web experience down and doesn't assist the search engine cause well at all either.
If you are building a web site in this day and age you should aim for the very best technology available to deliver your message. It may be a long time before you get a major web site redesign or make over; so why not start off with the smallest, most efficient code in the initial build?