Okay, as a "northerner" I am going to put in my 2 cts..... and I am not being critical of ANYONE...
Couple of questions.... can you go into your profile and put in the general area you are in? It gives a better idea to any and all of us about where you are, what your market is, what your pastures are what hay is grown in your area? Don't have to be specific... you can see under everyone's avatar most have an area or a state or something listed. I for one can not remember where most members are from one post to another...
Corrientes here in Va are used for both roping, and some bulldogging... most of the team penning here just uses smaller feeder calves but some have some "ear" cattle in them. Black is the "only color" here according to the buyers... and we see big discounts on ear cattle.... Not that I don't like them because I do. I have a longhorn for a "yard ornament" that is raising her 2nd calf this year... milks good, is a great momma and hates stray dogs etc in the field so a good "guardian".... raised a real nice black steer calf last year.... she has a pretty, colorful white w/black speckling heifer this year and I will keep her to be a cow most likely.
Don't know about the corientes being used for bucking bulls, most that I have ever talked to stock providers years ago had some ear in them but there are many members on here that know alot more about that than me.
If they do not discount the calves too bad there, then using the friends bull on your heifers for small calves is not a bad idea. You may not get real good prices... but if they have the calves with no problems then a live calf is better than pulling a dead one.
If you are going to raise any of them up for beef for yourself, then color won't matter.... and you can sell the nicest ones for feeders and keep the one(s) that are not as good and eat 'em.
The pictures are not a real good way to judge. But one thing, why keep a bull to only use on 3-4-5 cows.... he is going to be eating for another year, then you will get calves from the heifers from the friends bull, then he is going to be eating for another 3-6 months before he goes in to breed them back... all for a months worth of work.... in the meantime, you are going to have to keep him from deciding that one of them is just too tempting when she is in heat... and someone going over the fence... and yes, heifers will go looking too....
And friendly bulls can be a problem because they do not always respect your space... and then they get to be hormonal teenagers and respect no one... and someone can get hurt.
I am not saying this to be discouraging... just to let you have a little bit of experience from someone else... and not learn the hard way.
There are alot of people on here that can tell you the pros and cons of keeping bulls... and unless you have some way to keep them occupied, they can become a real problem....
And it is not financially practical to keep a bull around for a half dozen cows... Do AI after you build a chute to work them in.... choose from hundreds of different bulls in dozens of breeds... Pay 50-100 a cow to breed them and never have to worry about that straw of semen getting loose, or tearing up fences, or HURTING someone or getting on the road and causing an accident.... all of which might NEVER happen, but can happen....
Just from the pictures, I like the grey striped bull better than the reddish one.... and that is not being able to really see them.
Okay, that is my nickels worth of advice/suggestions.