I’m in a similar situation! Just started on 150 mg aspirin every night based on my private gynae recommendation. But I will be going to see another gynae (who is more experienced with high risk pregnancy) based in public hospital for second opinion. Based on the different studies for aspirin use to prevent pre-eclampsia and different guidelines, seems like there is a range of doses studied and used (from 75 to 162 mg) so probably that’s why there are different recommendations. In the United States they use 81 mg (1 tablet) or 121.5 mg (1.5 tablet) because the aspirin available there is 81 mg per tablet. In Singapore we have 100 mg per tablet.
Think there is no evidence currently on whether 150 mg is better than 100 mg dosing in terms of preventing preeclampsia and/or less risk of bleeding, but the general opinion is both are effective and reasonable doses. I will probably follow the dosing recommended by whichever gynae that I eventually intend on following up with for the rest of my pregnancy, be it 100 mg or 150 mg.