Hi

I see 3 advantages having a Link 88
- You have 2 separate buses (1 & 2) to go in both directions of your layout (assuming your CS3 is in a central location).
- You can select 5 or 12 V (I guess the CS3+ is 12 V by default but not sure) so you may use other S88 types (not from Märklin.
- you may use Bus 3 (the old style flat cable-based decoder)
These are not huge reasons and if you start from scratch the safest way is to use 12 V for noise immunity. In that case if you don't bother having only one Bus from the CS3 then go ahead and return the Link 88 and buy additional s88 AC
In my case one of my "S88" is coming from my turntable decoder (DSD2010 from DigitalBahn) which works only in 5 V so I would need a Link88 (and I have one).
Cheers
Jean

An additional point to highlight would be


The L88 has 16 ports that you may use as a simple S88 . i.e. you already have the capability of a S88AC

However, these ports may be configured as an 8x8 matrix to give you 64 addresses (i.e. the equivalent of 4 x S88s),
which may be of interest if you wish to have a tactile control board with 64 buttons.

I would not use the matrix ports with the traditional "ground rail return" track detection, however if you have discrete sensors like reed switches where both wires are returned to the L88 as part of the matrix , that reduces you need for additional S88s.
(Personally I would keep things simple and use a normal S88AC or S88DC for any actual track detection.)



Just a small word of warning,
It has taken Marklin a long time to get the firmware workable on the CS2, with one significant issue being the tendancy to forget the configuration if the unit is not powered on at the right time.
The CS3 is a bit better, however make sure you have your power on process/sequence in place so everything powers up at the same time.