[Basic]

I wanted to know what is the difference between the smartgun Accessory vs the modification ?

Does the modification give more dice ?

[All4BigGuns]

The modification uses mod slots and is internal. The accessory does not use mod slots and is external. That's the only difference.

[Mirikon]

The modification means you can still mount accessories on the top or underbarrel mounts. The accessory takes up a mount, but is much cheaper, especially with the more expensive weapons.

[Aryeonos]

The internal version is nice for pocket pistols up to some small SMGs, especially if you wanna go with the slim, concealable, quick draw idea. But yeah, since the modification version costs the same as the weapon it's only really good for cheaper weapons like pistols. If you can, go for guns that already have the integrated version.

[Basic]

They also have internal smartgun as an accessory.

[Aryeonos]

It wouldn't be an accessory then, would it?

[Csjarrat]

as it is listed under the firearm accessories (p322, Sr4a) i'm going to go with yes, internal smartgun is an accessory.

[Mirikon]

as it is listed under the firearm accessories (p322, Sr4a) i'm going to go with yes, internal smartgun is an accessory.

A holdover from the original book, which was before Arsenal.

[RHat]

The version in SR4A is there for when you don't have the modification rules available.

[Anarkitty]

The entry in Arsenal reads:

Smartgun System: This modification is the internal version
of the smartgun system (pp. 311–312, SR4).

(emphasis mine)

So if you don't have Arsenal, use the rule in the Core book, but if you own Arsenal then the rule overrides the Core book, because the Modification in Arsenal is explicitly stated to be the same thing as the "Smartgun System, Internal" in the Core book, just with more rules applied.

I do know people that would try to argue that they should be able to buy the Internal Smartgun System from the Core book and therefore it takes no Mod slots and doesn't require a Shop or the Armorer skill to install.  These people should be beaten soundly with a rolled-up copy of Arsenal.