One more time please Optiplex Vs Vostro

OptiPlexes are built with a slower-changing hardware set and have the option of US-based support for businesses/business-critical applicatons.

Vostros are cosmetic variations on consumer-grade Inspiron and Studio models, with mostly offshore support.

If you need the system for a business and need US-based support, don't skimp and buy the Vostro - buy the OptiPlex.  If you're willing to sacrifice support and component consistency for a lower price - but KNOW that's what  you're doing - then the Vostro may be an option for you.

DO NOT expect critical business-level support with a Vostro.

Optiplex usually has higher-end components.  Example from the first link:

Opti 755: ICH9DO chipset

Vostro 200: G33 chipset

In this particular case, it means the Optiplex can address up to 8GB of RAM, vs the Vostro's 4GB limit, just to start.  Also you have higher thuroughput, better latency handling, an IOP, and that is with just 1 part different. 

Now, let's throw the model up from the Optiplex of the same generation, the Precision T3400.

Precision T3400: ICH9-R chipset

Model up from the Optiplex's... but wait, it can address 16GB of RAM.  Well, what else is the difference?  Well, the Precisions hard drive controller, for one.  The T3400 can run a SAS6iR controller, which means it has an embedded hard drive controller processor (an ARM processor to be exact). 

I run a Precision 690, I work on Optiplex, Vostro, and the whole lineup of laptops.  There is a difference, in terms of real world performance, as well as strength of components, as you move up the lineup.  My 690, for example, the physical case's metal is almost 4x thicker than the case of an Optiplex, solid metal.  I could crack walnuts by just dropping its side cover.

A computer is a wildly variable thing, performance can be improved, or degraded, at times dramatically through the simplest little things.  And all too often, these things are not listed on review sites.