The decision whether to build a bespoke site or use an "off the shelf" package really depends on the functionality of the site as each has its advantages and disadvantages. If the site has custom functionality that cannot easily be purchased in a pre-built package, bespoke is probably the best option. If the site is a Blog or an online shop there are many packages available for little or no cost.
Generic Sites - Generic sites are good to use as they are cheap (often free), provide good documentation and are readily available. You know the solution you are getting is used my thousands of other sites and as long as it is quite a large package, there is usually a lot of support available online. Many open-source sites are now available, these allow the user to build additional controls which is useful if the intended site is a shop or a Blog but has some additional functionality.
Generic sites do however have some disadvantages. As many people use "off-the-shelf" packages, many sites end up looking the same (although there are usually different styles and templates available). These sites may one day become the "IKEA of the Web" with everybody’s site looking identical. It is important to not just use a generic package just to keep the cost down and hack the package to meet your needs, I have tried this and it gets messy, the interfaces between the components often gets out of sync and can result in "dll hell".
Bespoke (Custom Made) Sites - Bespoke sites main advantage is that you can get exactly what you want. You find a company, give them your specifications and they design and construct the site for you. This can result in exactly what you need for little effort. In my experience it doesn’t always work like this, as the picture below shows, the finished product is not exactly what was requested.
Bespoke sites are often quite expensive; if you plan on getting a site built I would advise you to follow the advice below.
1) Request the site is priced for the whole job and not on a "time and materials" basis. There are inevitably problems building sites, costs can spiral resulting in you paying much more than initially intended (Trust me I have been there!).
2) Ensure you have designed the site as well as possible, make sure you have listed ever single requirement. I have heard horror stories of companies charging a fortune for functionality that "wasn't in the spec". It is worthwhile researching basic software engineering techniques (especially requirements elicitation and analysis) to ensure you have covered all bases.
3) Make sure you will own the site after it is developed.
4) If required agree a support agreement with the site developer.
5) Use a smaller local company, the costs will be lower and the service should be more personal (and you can go check up on them if you do not feel much is being accomplished!).
6) Build it yourself, it may seem daunting, but web development really isn't that difficult, there are numerous resources for support. Learning web development really can help increase the revenue from your site. You never know you may forge out a new career path from it.
There is no right or wrong answer to the question whether to use custom or generic, the decision is the site owner’s decision based on the type of site in question. It is worth investigating the options thoroughly as the wrong decision can be a costly mistake.