The USER who clicks on your link determines how a link will be shown, by setting preferences in his/her own browser. The choice (in browsers I've looked at) is to open links in the same window, open links in a new tab, or open links in a new window.

The most common setting is to open new links in the same window - where here "new" just means the next window you click on. This setting avoids the inadvertent accumulation of bunches of open windows during general browsing on the web, which might choke your computer.

Any user who wants to, with this setting, can still right click and choose another option.

Regardless of how much you prefer one or the other, new window or new tab, it is the height of conceit to insist that your website (or your posts here) must force viewers to do it exactly your way, unless you have a valid reason for doing so.

About the only really valid reason for forcing a new window would be when a secure connection is required for the exchange of personal information, since a separate instance of your browser is theoretically "more secure" than when secure and unsecure pages are open together in the same instance. (The difference probably is mostly theoretical.) You must also assume that the user/viewer is very likely to want to return (or you really want them to return) to the unsecured pages on your site (e.g. to finish shopping for your valuable sales offerings).

Many sites also open a new window for a "printable version" (and often open your printer driver for you) on the assumption that you will ALWAYS want to close the print driver and "printable" page, and return to the "real page." This usage is sufficiently common to be considered almost "standard practice," although it's far from universal.

Before tabbed browsing was universal, and when many users had such limited computer resources that they couldn't open more than a couple of windows at a time, you could probably assume that every click would result in display of the new target in the original window. In that long-gone era, it might have seemed/been courteous to write links with a "new" attribute. It's likely now to annoy as many people as it really pleases, except in the customary "secure exchange" and "printable page" cases (IMO).

John