How to choose a BMW ICOM cable

which a BMW ICOM cable you need: K+DCAN or ENET or BMW ICOM A2/ ICOM Next?

In summary,
It depends on your purpose (diagnostic or coding or programming) and model (Exx or Fxx or others).
For Coding, you need different Tools, NCS Expert / SP-Daten for E-Series and E-Sys / PSdZData for F-Series.
All Diagnosis and Coding can be done with cheap DCAN Cable for E-Series and cheap ENET Cable for F-Series.
For Programming (Flashing ECU’s with new Firmware), then you need ISTA/P for for both E-Series and F-Series cars, or you can use WinKFP for E-Series and E-Sys for F-Series. For E-Series Programming, you will need an BMW ICOM, but for F-Series Programming, you can use ENET Cable.
For Exx- Series:
Interface = K+DCAN Cable (OBDII to USB) or ICOM
ECU Data Files = SP-Daten
NCS Expert = Coding Software
WinKFP = Programming (Flashing) Software
EDIABAS = Low-Level ECU Communication Software used by NCS Expert & WinKFP
For Fxx- / Ixx- / Gxx-Series, Mini, & Rolls-Royce:
Interface = ENET Cable (OBDII to RJ45 Ethernet) or ICOM
ECU Data Files = PSdZData
E-Sys = Coding Software
E-Sys = Programming (Flashing) Software
About: BMW ICOM
ICOM A (also ICOM A2, ICOM A3, ICOM Next A): main interface
ICOM B: adapter for programming multimedia in E series
ICOM C: adapter for old BMW with round 20 pin diagnostic plug
ICOM D: adapter for motorcycles
ISTA+ (AKA Rheingold or ISTA-D)
DIAGNOSTICS for All Vehicles
PROGRAMMING for F/I/G/RR & MINI, but requires an ICOM
ISTA-P
PROGRAMMING traditionally for all chassis, but is being phased out by August 2017, except for legacy E-series.
Replacement ECU's must be NEW
YOU HAVE TO KNOW before you buy ICOM A2 or ICOM A3 or ICOM Next:
ICOM NEXT vs the old ICOM
-> much faster in BMW F and G series ..
-> supports gigabit Ethernet too to be future proof, there currently is not gigabit Ethernet protocol defined yet for autos. Also it has USB3.0 instead of USB2.0 and a better wifi card.
ICOM NEXT A vs ICOM A2
-> more stable during programming
-> be necessary for the future Gbit cars
-> faster start-up times and high throughput
-> through high-performance,low-power ARM SoC
-> improved handling
-> more flexible OBD cable
-> lighted button for logs
…
ICOM A vs ICOM A2 vs ICOM A3
Modified ICOM A2 for vehicles with OBD access receives a significantly more powerful processor and more storage capacity. And robust aluminium case will help to avoid damage when using in harsh environments. It works better in cooling, runs faster and works more stable, not easier broken than older BMW ICOM A+B+C.
ICOM A3 can program all units for all BMW series expect media system, and work more stable and has stronger compatibility than ICOM A2, A1.