What to choose a responsive layout or a mobile version of the site? It is not possible to answer this question unequivocally. Each approach to this problem has its pros and cons.

Let's first figure out the difference between "Adaptive site layout" (adapted site) and the mobile version of the site.

A mobile-friendly website, a responsive layout, a responsive website is one and the same concept. Implies that the site is using CSS for the user's specific screen resolution. The "Bootstrap" libraries are very often used, which is very convenient for site layout. Examples of sites with adaptation, which use adaptive layout: Wildberries, DNS, M.Video. These sites use a responsive layout. But "Yandex.Market", LaModa, use mobile version of the site.

Let's try to figure out the better both of them.

Adaptive layout will allow you to get rid of the development of a separate version of a (mobile) site, which in turn entails high development costs and site content. For the mobile version of the site and its desktop version, the same Internet address is used, which in turn will significantly reduce your advertising and promotion costs of such a site.

The mobile version of the site uses a different address than the desktop version. It can be either a subdomain (mobile.site.ru) or an additional directory of the site (site.ru/mobile/). In either case, this is an additional cost of hosting space, hosting resources, which in turn does not play a special role.
The mobile version is more flexible. It can be facilitated as much as possible, speed up the loading of the site for users of mobile devices. User can switch freely between mobile and main versions of the site.

In some adaptive solutions, it was noticed that the page code contains two versions of the code for the same blocks (desktop and mobile) at once. Those. depending on the use of the device type by the user, one or another site code is loaded, the unnecessary (rest) code is hidden with the help CSS properties (display: none). This method can play a bad role and can lead to problems with the indexing of the site by search engines, which in turn are not very love "Doubli", because when crawling pages, the search engine robot sees the page code completely regardless of the user's screen resolution. And such a site is immediately marked them as a site with "duplicates" and can get on the sanction of a search engine. The browser reads the entire year of the site, and repeating blocks, regardless of CSS properties, can slow down the page loading process; scripts that are necessary for the functionality of the hidden block can also be loaded.

Why is using responsive website design instead of the mobile version one of the right decisions?

From the point of view of promotion, a site with a responsive layout wins significantly over a site with a mobile version in that it has the same address, there is no need to promote both versions. Quite a convenient solution for website promotion in several regions.

Cons of the Mobile version of the site.

Mobile development costs are higher.
Increasing the cost of a separate promotion of the mobile version, you have, in fact, to move two sites instead of one. It is more difficult to do analytics and develop the right promotion strategy.
A complete mess of "quick links". Both versions of the site download 99% of the content from one database. When downloading the mobile version, the content may links to the desktop version of the page are displayed.

Which option should you choose? Website with responsive layout or mobile version?

If you are planning to create a business card site, landing page, showcase site or catalog, from experience we can say that the site with adaptation in your case looks more the right decision. Only initially decide on the functionality of the site so that you do not have to hide part of the content when the user visits it from a mobile devices.

If you have a serious project, an online store with a voluminous catalog, with user reviews about products and the like, i.e. with an extended functional set, consider creating a mobile version.

In the end, it doesn't matter which decision you come up with. This is purely your choice.