Hi Ctelly
Congrats on your pregnancy!
At the end of the day, it's a personal choice that only you can make. I still say that any way your baby is getting bm is better than formula, be it by exclusively pumping or combining the two BUT I can only speak from personal experience now.
A pump doesn't come close the sucking of a baby and every mommy reacts differently to a pump. Some get more out from a manual, than an electric or vice versa. Some get more out from hand expressing but you need to know that what you get out is no indication of your milk supply. Your baby is far more sufficient in draining that boobie.
It will also depend how well you get a letdown for the pump.
Why do you want to pump instead of feeding directly? Is it to make things easier when going back to work? Pumping to me is such a schlep and also hard work cause you need to wash bottles, sterilise them etc. It's a different story when you have to pump during work and washing it but doing it 24/7 is a different story.
The downside of doing it can be that your milk can decrease if you struggling with the pump, you will have to pump at least every 2 to 3 hours to keep supply up and most important con is that you taking away that mothering tool for baby

I can't explain to you until you've experienced this for yourself.
I never bm my daughter but I was determined when I fell pregnant with my son. Yes, the first few weeks are hard but it's soooo worth it in the end. Your breasts are nature's natural dummy. It calms them down, it's their security, their comfort, helps them fall asleep, helps when they teething etc. I enjoy it so much and it really is just so easy and convenient to whip it out.
The La Leche League Leaders have a saying "when in doubt, whip it out!"

hahaha
If you also trying to pump earlier to get baby used to a bottle, don't let it stress you out so much. You can really start introducing a bottle about 2 weeks before returning to work and let someone else give the bottle. Some babies take to it easier than others and others baby just plain out refuse a bottle but you can introduce cup feeding or even a sippy cup. You even get babies who happily wait for mommy to return home and top up like that and some will drink just enough during the day to take the edge off.
If you won't be able to express at work at all, then express over weekends and every other time at home when you can.
I hope this helps a bit. I need to fetch my kiddies but please feel free to ask away!