I recently got the Speedy B 25 and my hope is to use it as an everyday bag while home and while traveling (working out well so far while at home, obviously haven't traveled yet). It will not fit a laptop though and I don't think it will fit my iPad Pro (although haven't tried). You mentioned that you don't need this to be your day-to-day bag and it sounds like you'd want to fit a lot in this not only while you're in the process of traveling (like on the airplane), but also while sightseeing. Do you plan to carry larger electronics with you when you travel? If so, I don't think you'll be able to fit them in either size Speedy and you might have to bring another item on the plane anyways. If I'm traveling and have to bring my laptop, I plan to just use my MZ Wallace Large Metro Tote on the plane, which I could place my Speedy and my laptop in. Then, I'll use the Speedy once I get to my destination.
I also personally think the 30 looks too big as a crossbody, so I wouldn't want to carry something that big day-to-day while traveling. I do think it looks great carried on the shoulder or in the crook of your arm. Either way I really don't think you can't go wrong! When I was in the process of deciding, I looked at Instagram posts tagged #lvspeedyban25 and #lvspeedyban30. There are lots of model pics to see how it looks on people. Good luck!
I also personally think the 30 looks too big as a crossbody, so I wouldn't want to carry something that big day-to-day while traveling. I do think it looks great carried on the shoulder or in the crook of your arm. Either way I really don't think you can't go wrong! When I was in the process of deciding, I looked at Instagram posts tagged #lvspeedyban25 and #lvspeedyban30. There are lots of model pics to see how it looks on people. Good luck!