It depends:
1. An all-in-one radio like the 7100 is a cost effective solution that provides SSB mode on 2m/70cm as well. Still, 2m/70cm SSB may not be popular in your area and the antennas used for that mode are typically horizontal. I have a ”shack in the box” radio, but I also use it for the ARRL VHF contest where 2m/70cm SSB is popular. Also, if you prefer to focus on one radio audio at a time, this would be satisfactory. An Icom 7100 is a popular choice.
2. I typically have a VHF/UHF mobile scanning various frequencies while I use my HF radio. I do not mind the combined audio in my ears, but when I am seriously contesting only the HF radio is turned up as I am focused on that. Still, my main hobby is listening, so I typically enjoy dialing around on a separate HF while my VHF/UHF scans. Some operators find all that simultaneous audio distracting. What is your preference? If unsure, perhaps go slow.
Starting off with an all-in-one would not be foolhardy. If you later find yourself actually wanting a mobile you would actually use in the vehicle, and or at home, the cost later is not outrageous. Ultimately, if you have the space and means to put up an HF antenna, or two, as well has a VHF/UHF antenna on your roof or a mast above your roofline the shack in a box 7100 radio may be suitable.
$800 - Icom 7100 + maybe $300 Icom 2730 later
or
$900 - Icom 7300
$300 - Icom 2730