Yes and no. SEO is a complex concept, but I'm going to narrow down to removing content:
If you have a modest amount (e.g. ten pages) of content and then delete a regular page, you will probaly notice that because you've removed 10% of your pages.
If you delete high quality content, pages with high amounts of visitors or pages where people spend a lot of time on, you will notice this.
If you have a large website (e.g. 1000 pages) and you remove that same page, you've now removed 0.1% of your pages.
In both cases you will loose some PR, yes. The quality of that page and the size of your site determines how much.
The counter argument for keeping the pages is for your visitors. What if they go to your page, but the page now says "Discontinued!". Would this have a negative effect (if so, delete the page) or a positive effect because you inform your clients (then keep the page).