From Mali Lošinj (recommended)

(+) Pluses

• much more flexible to come and return since you can leave from Susak to Mali Lošinj at least 3 times a day. 
• there is always possibility to pay for taxi boat and come fully privately
• it is good to have a car on Mali Lošinj – you can go shopping, or make one day trip
• in case of a bad weather (which is not likely during summer) there is a greater possibility that you will cone to Lošinj then to Rijeka
• you come to Susak earlier (not only in evening)
• no ticket reservations needed

(-)  Minuses:

• More expensive (you have to pay for ferry to Cres)
• Longer drive, especially for people coming from abroad
• You have to come to Croatia much earlier during the day of arrival since the afternoon ship sails out at 13:00

Sailing schedule

Jadrolinija lines for those coming over Mali Lošinj:

• Valbiska – Merag  car ferry to Cres/Lošinj over Krk – for those coming from direction of Zagreb (Hungary, Slovakia, Eastern Austria)
• Brestova – Porozina car ferry to Cres/Lošinj from Istria – for those coming from direction of Istria (Italia, Switzerland, Germany)
• Local ship line Mali Lošinj – Susak – Unije – which goes twice a day

currently valid schedule can be found on Jadolinija website

• Pula – Unije – Susak – Mali Lošinj – Zadar  fast catamaran line which you can use to come from Pula or from Mali Lošinj in the evening. Sailing schedule can be found here

Private transportation (Taxi Boats) – here are some of them for which I know that are reliable:

• Nedoklan – this guy goes when the weather is really bad
  • 1h needed from Mali Lošinj to Susak
  • mobile: +385 98 7241 83
  • price on inquiry
• just Google taxi boat Lošinj and you will find additional options

From Rijeka

(+) Pluses

• more convenient especially for guests having a long drive to Croatia
• you can arrive to Croatia much later since Catamaran is sailing out at 17:00 
• once you are on the Catamaran your vacation starts:)

(-)  Minuses:

• more unreliable – in case of a bad weather it is more likely that Caramaran will not sail, but local lines are
• ticket reservations are needed in an advance

Sailing schedule:

• Catamaran (Rijeka – Mali Lošinj)

From Pula or Zadar (over Mali Lošinj)

As said earlier this line is useful to come and go to Mali Lošinj, however some of the guests use it to get to Pula or to Zadar to continue their vacation

Sailing schedule can be found here