I can only make suggestions based upon having attempted G1, which shares the G2 route up to C1, and from friends who have summited and/or guided the others. Despite all I write below, I'm not really comfortable giving 'advice' about peaks I have not been on.
Consensus is that G2 is harder than it used to be:
- due to changes in the ridge. ie. steeper and icier, esp in the Banana section
- due to similar changes in the last part of the summit ridge, making it thinner/steeper.
Note that to some extent this 'consensus' must take into account the gradually declining experience and skill of most 8000m commercial clients, and most commercial mountaineering clients in general, particularly on the Seven Summits. This is not necessarily a harsh criticism, more just the current reality that guides and companies are gradually dealing with (prep courses, more O2 use, more ropes, more Sherpas etc). Most of the 8000ers got their reputations 20 years ago, when the climbers on them were quite different from those on them today. Remember that the much-derided initiator of the Seven Summits, Dick Bass, did Everest in 1985 without fixed ropes above the South Col and on 2 litres a minute O2 (normal now is 4).
On G2 in 2007 an avalanche fell from near C2 down the slope beneath it and two people were killed (Amical clients). So now prospective G2 climbers probably need to consider increased objective danger on the route, which was not considered a factor before. Like all things in the mountains, this may change, or not.
ChoOyu is still considered the easiest of the lot, whatever 'easy' means on big Himalayan peaks. Realise that to some extent this stuff is a self-fulfilling prophecy. If lots of people think a peak is easy they will go there, and increased numbers means broken trails, established camps and probably lots of fixed ropes, making the whole thing easier. Doing ChoOyu on your own with just a few mates and no one else on the mountain would be very hard.
Manaslu is technically easy, except for the summit ridge that many do not really finish - but the route has serious objective danger down low from serac fall, and also from avalanche. There is also crevasse danger not present on ChoOyu. The upper plateau is no place to get lost in a whiteout, several have died here. Manaslu was unpopular because of the objective dangers, but this has changed in recent years due to the politics of ChoOyu and the need of commercial guiding companies to have an 'easy' 8000er for clients to do as prep for Everest.
Shisha also seems to be 'easy' but if you can't climb that last corniced ridge or loaded snow slope to the highest point then you're not really climbing the mountain. Hence the drop in popularity of Shisha in recent years, plus the politics.
Broad Peak is a relatively direct route, but with some objective danger. Again, many do not go to the summit, they stop far away at the rocky forepeak, due to the length of the summit ridge, so it is certainly not straightforward. BP is a good example of a peak that got its reputation years ago when its suitors were stronger than today.
Remember also that the Baltoro 8000ers require an 8 day walk in up a hot, dusty then cold valley with no trekking lodges offering apple pie and beer. ChoOyu you drive to BC and go to C1 in hiking shoes.