I am currently on H1 B (since October 1, 2017). Last year when on F1 OPT, I had filed Form 1040 NR for my taxes. Which form is advisable for 2017, considering I am on H1 B now. What options do I have?
By default, you are a nonresident alien for all of 2017, because you don't satisfy the Substantial Presence Test for 2017. You are an exempt individual (exempt from the Substantial Presence Test) for your time on F1 status in 2017 (you hadn't been an exempt individual for some part of 5 previous calendar years; only 4 -- 2013, 2014, 2015, and 2016). Therefore, only the 3 months you were on H1b count for the Substantial Presence Test, and it's not enough to pass.
You have the option to use First-Year Choice when you meet the Substantial Presence Test for 2018 (which will happen some time close to the middle of the year, as days from the previous year only count as 1/3, so you will need about 5 months from 2018, in addition to the 1/3 of 3 months you had in 2017, to meet the Substantial Presence Test for 2018). This will make you a dual-status alien for 2017 -- a resident starting from when you started H1b, and a nonresident before then.
If you are married, after using the First-Year Choice to become dual-status, you can choose to further use the Choosing Resident Alien Status or Nonresident Spouse Treated as Resident option to make both of you resident aliens for all of 2017, and you guys must file jointly.