The BA/VS debate is always going to be a personal decision and not one that anonymous forum dwellers can make for you.
Direct entry on BA LH will mean losing every weekend for years, having very little bid satisfaction for a long time, huge blocks of reserve and a lot more time away from home as trips can be up to 9 days long and fewer mandatory days off after duties. Some of the junior 777 rosters are eye-watering. The trade off is that the trigger for 3 pilots is a lot lower and more trips attract more time downroute, so your work life gets easier at the expense of your home life. There’s also a much larger route and fleet network and many more pay scales so the likelihood of getting bored of the job is less in the long run. At the end of the day, owned by IAG, BA aren’t going anywhere. Allowances are much better as well.
At VS, the rotating bid groups work well (unless you’re on the 350 which is chronically understaffed at the moment) and mean that every three months you should have a successful roster bid. Also rotates for annual leave so every 3rd cycle (leave bid cycles are for half the year) you should have a successful leave bid. The mandatory three days off after long two pilot duties that the new deal protects is great, as well as the east-west transition rules. Although after they get rid of the 333 we’ll see an increase in 3-pilot, 2 RDO trips (more akin to BA). Another perk of VS is that if no exterior disasters happen, you are looking at 7-8 years for a long haul command, roughly a decade quicker than at the other flag waver. The downsides are that the route network is a LOT smaller, there is no fleet bidding, you get what you’re given. As it stands, over winter the 787 does most of the interesting routes, MLE, CPT, JNB, PVG etc. The 330 takes most of the Caribbean and east coast workhorse stuff and the 350 does the west coast, LOS and India. Again, you have no choice in what you get. Those on the 350 with flexible schedules can earn thousands a month in overtime just moving duties around a couple of days, overtime on the 330 doesn’t really exist at the moment. All subject to change if the fleet structure changes.
Personally, my opinion is if you’re young and single and want to stay in the UK, BA is your best bet. However, if you have family you enjoy spending time with or are joining a bit later in life VS is a great option. Majority of people at Virgin are a pleasure to fly with and just want to have an enjoyable trip. You’ll almost always find someone to have a beer with or fill your downtime.