Very briefly, and current state of affairs - can easily change! - 73 means LGW. More "day trips", less long tours, than Airbus @ LHR.
People do "commute" for SH, but it is hard work, and no Staff Travel for first 6 months. In SH, and junior, you will spend a lot of extra UK nights because your report is before the first inbound flight arrives, or last flgiht has gone by the time you clear.
Rule #1 for any seniority based company is join ASAP - sort out fleet / lifestyle once you are "in". Plenty of people joined having been offered LH and ended up on SH... Shame to have also cost yourself hundreds of seniority places as well
HTH
NoD